(FORTUNE Small Business) – Maybe you're getting your teeth cleaned when it hits. Or sitting at home watching Regis trying to extract that final answer from yet another aspiring millionaire. When that eureka moment strikes and the great new idea dawns, the where doesn't really matter. Unfortunately, the when does. And it doesn't take a genius to understand that this isn't the booming era of just two years ago, when a roaring economy created ever-higher waves of investment bucks.

Common sense would suggest that it is hardly the best time to be dreaming up a great new idea and starting a company to exploit it. But since when did common sense ever apply to entrepreneurship? True, timing matters if you're defusing bombs or if there's a roomful of people waiting for you to say "I do." But company building is supposed to be a counterintuitive, even radical act. "For the right ideas this is a great time," says Gary Hoover, a serial entrepreneur who is about to launch his next venture (to see how he defines a great idea, see "My Next Business"). "It's a great time to seize the opportunity."

In fact, challenging economic periods have consistently proved to be good times to launch new businesses. Sixteen of the 30 companies whose stocks make up the Dow started during recessions. General Electric traces its roots to the panic of 1873. William Hewlett and David Packard founded their eponymous business during the Great Depression. Ancient history, you argue? The year 1982 didn't look like such a great time to launch a technology company: The U.S. was in the midst of a recession and unemployment was at its highest since World War II. Seems the founders of Sun Microsystems, Compaq Computer, Adobe Systems, Silicon Graphics, and Lotus Development disagreed. All those companies started up that year--and prospered.

How did such big-name companies buck the odds? Ideas--the good ones, anyway--are always in demand. And now is a perfect time to take your idea and run with it. It sounds illogical, perhaps nonsensical, but the simplest way to put it is this: In good times you'd never have it so good.

These days, it may be easier to raise startup money than it was during the boom. No, it doesn't seem that way. But that's a perception promulgated by precarious or now deceased startups. "The companies founded two or three years ago have been struggling with the assumption that follow-on investments would be as easy to get as the initial funding," says Geoffrey Moore, venture capitalist and the author of Crossing the Chasm. "They're not getting [the follow-on] funding, and so they're telling people that VCs don't want to spend. We do, but more on the traditional companies missed during the dot-com bubble."

While there's no question that the moneymen are keeping a close watch on their wallets and asking a lot of questions, that kind of vigilance actually works in favor of the smart entrepreneur with a bright idea. Anyway, there's a difference between a cautious investor and an empty-pocketed one. "People are sitting on millions of dollars," says Jack Derby, founder of Derby Management, a Boston-based consulting firm that specializes in helping venture-backed companies. "The upside is that the money isn't already gone. It's still there." According to venture capital watchdog VentureOne, VCs raised $39 billion in the first three quarters of 2001 but have invested only $25.5 billion of it.

Hard times are also boon times for wading into the talent pool. "In rapid-growth times it's hard to get the right people--you're more likely to compromise on who you get," says management guru Jim Collins, author of Good to Great. But in a recession a new company can land better-qualified, less expensive employees than at other times. Indeed, with everything costing less, you can ask cautious investors for less, showing your prudence and making you a more attractive prospect.

As always, businesses that can help solve the day's most pressing problems stand the best chance for success. "A roaring capital market is not a critical ingredient," says Charles Holloway, co-director of the Center for Entrepreneurial Studies at Stanford University. "What you need are ideas that address a critical need in the marketplace." Sun's workstations enabled buyers to lower costs and boost efficiency just at a time--the recession-plagued early '80s--when cost cutting and increased efficiencies were imperative. "In hard times big companies stop investing in R&D," says Collins. "That opens doors."

With that in mind, we asked some of the best-known opportunity identifiers to tell us about their next big idea. There's a reason these folks made it big in the first place: All their ideas address a specific market. But how clear are those niches, and how well do these ideas fill them? Just remember, with their prominence, these entrepreneurs can easily raise the cash to put their notions into motion. Harder--for them and for you--is finding the right idea for the right time. That's the dream juncture. And who knows? Maybe you'll beat them to it.

Fred DeLuca Founder, Subway Restaurants

His next business? Mr. Wonderful home-repair service.

Elevator pitch: A Mr. Fix-It to find all your Mr. Fix-Its.

Upside: No one wants to hunt for a good housepainter.

Obstacles: No one wants a lousy housepainter either.

When Fred Deluca moved to Fort Lauderdale a decade ago, he noticed that his neighbors had incredible extended families: Tradespeople hung around their homes like so many clingy brothers-in-law. He realized there might be a business in easing the hassle of finding such home-repair help.

Enter Mr. Wonderful. DeLuca's idea is to have a single place for homeowners to call to get all their home-improvement tasks done, whether they need a wall ripped out, a carpet cleaned, or a heating system repaired. Mr. Wonderful can pull off this trick because he--or, uh, it--has partnered with trade companies in the area to provide those services. The contractors do the work; Mr. Wonderful gets a cut of, say, 10%. To ensure quality, contractors in the network would agree to abide by a Mr. Wonderful code that would stress--no, demand--customer satisfaction.

By hooking customers up with a specific contractor, DeLuca's service wouldn't give users the ability to shop around, which means he's not going to be Mr. Cheap. DeLuca hopes to minimize the problem by targeting upscale neighborhoods.

The last word: Love to use it, wouldn't want to run it. Do you want the headache everytime a plumber doesn't show?

Leonard Riggio Founder, Barnes & Noble

His next business? Personal assistants for the (almost) masses.

Elevator pitch: If Batman time-shared Alfred.

Upside: Who wouldn't want to live like Oprah for a day?

Obstacles: Oprah doesn't share her assistant with 24 others.

It's a special sort of person who likes to do his own grunt work. And we're still searching the nation's mental institutions to find him. Usually you have to win an Academy Award or engineer a Wall Street buyout to hire a lackey, but Riggio wants us all--or at least those of us who can justify shelling out a couple of grand or so a year--to be able to outsource our speed-dialing.

To whom, exactly? The personal agent, as Riggio calls it, is an on-call advisor and gopher. Need to find tickets to a play, reserve a car, buy the spouse a gift? "You just pick up the phone," says Riggio. Your not-quite-personalized agent would serve at least 25 clients. And the firm would also earn fees from the companies hired to do the catering, car detailing, and so forth.

The downside, obviously, is that your personal assistant is personal to all those other clients too. Riggio says the shared system wouldn't prevent assistants from getting to know their clients; a thorough pre-interview would take care of that, as well as making sure the client didn't have unrealistic expectations. If not, clients may need to hire a personal assistant to prod their personal assistant. The success of Riggio's service would also seem to rely on a healthy economy. When times are tough, a semi-personal assistant is likely to be the first luxury to go (right after you eBay your Segway Personal Transporter).

The last word: Time-sharing? Vacation homes and jets, yes. But assistants? Why not? After all, you can never underestimate the laziness of the American consumer.

Keith Clinkscales Chairman and CEO, Vanguarde Media; Founding President, Vibe

His next business? Interactive digital superstores.

Elevator pitch: Best Buy: The Next Generation.

Upside: Converting millions to emerging technologies.

Obstacles: Tom and Nicole got along better than the big-business partners he needs to make this work.

If you're one of the four people still listening to Supertramp on eight-track and watching Battlestar Galactica on Betamax, skip to the next entrepreneur. As most of us know, the entertainment industry is in the middle of lapping us again, as music and movies go digital with the increasing popularity of MP3 music and DVD players.

Clinkscales envisions a new kind of entertainment superstore that would educate, entertain, and elicit desire to buy into the new generation of digital media. Buy a new Apple iPod MP3 player and head over to a kiosk where someone helps you stock it with tunes.

Of course, Clinkscales must woo not only technophobes but also savvy consumers who already know how to download music. To lure them, he envisions a place that is "as close to a theme park as you can get," where space is designed "to encourage the maximum visual excitement."

The excitement may get customers in the door, but to open their wallets, Clinkscales sees a series of smaller rooms off the main floor where sales assistants would instruct them on all the latest toys and show them how to download--and buy-- content for their PCs and MP3 players.

Getting the digital content--so vital for differentiating the store--will prove tricky. Clinkscales needs partnerships with music conglomerates like Sony, outfits that haven't exactly shown a lot of desire to be cooperative (think Napster).

Clinkscales fully expects existing chains to retool to respond to the market transition, but a company starting from scratch would have a significant edge over the Blockbusters of the world.

The last word: If it's as cool as it sounds, heck, we'd wait in line for this. But no digital music, no ka-ching.

Tim and Nina Zagat Founders, Zagat Survey, restaurant and entertainment guides

Their next business? A fee-based online political forum.

Elevator pitch: Pay to have your say.

Upside: The Zagats made restaurant reviews page-turning reading.

Obstacles: Isn't this what talk radio is for?

Tim and Nina Zagat know there's power--and profit--in venting. Their best-selling restaurant guides comprise reader ratings and comments. "People want to be able to express themselves responsibly and know their voices are going to be heard," says Tim. And not just about the pasta primavera.

Subscribers to the Zagats' online town halls would pay an annual fee of about $15 to voice their political views. Results would be given to the relevant media, politicians, and other interest groups. Unlike typical polls, there would be no statistical projections or random sampling, and the Zagats' forum would let participants write in their own rationales along with a yes/no answer.

But it's debatable whether issues like stem-cell research can stir more passions--or attract enough customers--than who serves the best filet mignon. The Zagats dismiss the notion of charging influencers to receive the results, although doing so would open up a second, more predictable revenue stream.

They may not have to pay for it, but the success of the venture depends on politicos' and other influencers' acceptance of the validity of the results. Why should an elected official heed comments on the site? "If you look at who goes to the polls now to vote, that's self-selected too," says Nina.

The last word: People may relish heaping discomfort food on politicians, but they could choke on paying to do so.

Earvin Johnson Chairman and CEO, Magic Johnson Theatres and Johnson Development

His next business? Small, secure housing communities for the underserved.

Elevator pitch: The house that Magic built.

Upside: Urban middle class an untapped market.

Obstacles: Untapped? Or uninterested?

Earvin "Magic" Johnson understands the urban market. His Starbucks franchises offer not just scones but sweet potato pie too. His TGI Friday's outposts have sour-apple martinis that aren't available throughout the chain. Tapping a market's desires is how Johnson scores in business: His 29 coffee spots rank among the top performers in the chain. And now Magic's bullish on housing--but who isn't? Interest rates are low, and people are always looking for a better place to live.

Yet Magic has a plan to differentiate his housing units. First, there's the market he'd pursue. "The biggest opportunity for anybody is in the Latino and African-American markets, because you don't have as much competition and the real estate prices aren't as high," Johnson says.

With housing, the key would be to leverage an understanding of the market and its needs, to deliver what competitors overlook. Johnson sees the urban middle class he'd be targeting as having clear desires: a safe, secure building in a playful environment. Keeping the number of units per building low--say, four or so--would simplify and shore up security issues.

But residents are going to want more than cozy spaces where they're not battling 100 tenants for an available washing machine. "It would have some Magic Johnson signature to it," Johnson says. Right now, he's not sure what that would be, though he's not ruling out a pool or tennis court. More likely, however, would be some sort of common party or recreation room, housing a pool table, Ping-Pong, and room for about 30 friends. Johnson has long stressed the need for urban meeting places, and the success of his coffeehouses and movie theaters show there is a demand. "People want to have some fun in the confines of their own home so that they don't have to go out," Johnson says.

There's another strength Magic could play up. Inner-city developments have traditionally lacked nearby amenities. With his growing empire--his most recent buy is the Fatburger fast-food chain--Magic could fill the need with his own businesses.

"Look, I'm not coming in here with anything magic," he says. "All I'm trying to do is go where there is a need and a want."

The last word: He builds, he scores.

Paul Orfalea Founder, Kinko's

His next business? Emergency-supply stores.

Elevator pitch: Home Depot for survivalists.

Upside: No one's laughing at those Y2K zealots now (much).

Obstacles: Backup generator or Xbox? Choices, choices.

Paul Orfalea made his mark bailing customers out of photocopying jams. Now he wants to help them out of more dire situations. Since Sept. 11, disaster relief has been big news, but Orfalea sees an opportunity to make it big business too. His emergency-supply stores would sell generators, first-aid kits, food, and antibiotics, among other life-saving gear. He would have staffers, possibly even specialists from the Federal Emergency Management Agency, train customers on the equipment and on safety procedures.

Selling the gear would be only the first part of Orfalea's revenue stream. He'd also hope to sell customers on a kind of personalized emergency management. Charging a monthly fee, he would send employees to homes, setting up and maintaining generators and other devices and checking that the food stash hadn't gone stale. "So if there's any disaster, it's sort of brainless for the individual," says Orfalea.

The last word: Orfalea may want to save lives, but he risks looking like he's profiting from America's newly acquired fears.

Hilary Billings Chairman, RedEnvelope, gift catalog and Website

Her next business? Stylish accessories for geeky gadgets.

Elevator pitch: Sex and the City goes to Comdex.

Upside: Always a new gizmo to clothe.

Obstacles: It's a pocket organizer we're talking about dressing up, not Jennifer Lopez.

Just because you own the latest all-in-one cell phone, PDA, and pager doesn't mean you favor a Jetsons aesthetic. Colored plastic and brushed titanium aren't for everybody--how about a pouch for your BlackBerry in saddle-bag leather or an adjustable oak laptop stand?

"I'm interested in a company that will develop more functional, stylish accessories for all this technology in our lives," says Billings, who built her career at Pottery Barn and W Hotels meshing the stylish and the functional.

While retailers have addressed some of this demand--Coach makes calfskin cell phone holders, for example--no one has built a brand on making handsome tech accessories that don't look like props from The Matrix. Still, cultivating an entire line of products could be daunting (read: expensive). Teaming up with a particular manufacturer--becoming the exclusive outfitter of Motorola gadgets, for example--would streamline the business.

Of course, with technology changing so fast, today's elegant Palm case may someday (soon) be as relevant as a walnut shelving unit made just for your Atari 2600. And at least the shelves will hold your videotapes of JAG.

The last word: Style counts, but how much will we pay to outfit a gadget we'll replace in six months?

Mark Cuban Founder, streaming-media hub broadcast.com; Owner, Dallas Mavericks

His next business? Developing add-ons for high-definition televisions.

Elevator pitch: High-tech TVs need high-tech accessories.

Upside: A potentially huge market means a potentially huge opportunity.

Obstacles: Do you know anyone who actually owns an HDTV?

Contemplate high-definition television and you're likely to think of two clear business opportunities: making the sets and creating the programming for them. For the entrepreneur neither is particularly promising. Cuban--no stranger to HDTV, having launched HDNet, the first nationwide high-definition broadcast network last September--sees a third possibility: everything else. "There's a lot of opportunity for add-ons and utilities and third-party connectivity tools," he says. "There isn't a rich integration market yet." Cuban thinks even something as modest as the cable to connect an HDTV to cable set-top boxes could be a winner.

Making HDTV accessories won't get you dates with starlets, but history is filled with humble but lucrative TV accessory inventions. Marvin Middlemark, the archetypal eccentric inventor (he held a patent for a water-powered potato peeler), created and manufactured the rabbit-ears television antenna in the 1950s. A decade later he sold his company for $5 million, nearly $30 million by today's standards.

Of course, barely anyone owns a high-definition television today. The chief culprit? Prices, which average just under $2,000 a set. Cuban points to several factors that heighten his HD boosterism: Costs are dropping, sales increased 84% from 2000 to 2001, technologies like DVD have whetted viewers' appetites for high-quality images ("Why did people switch from VCRs? DVD looks better. And the quality of HDTV is triple or quadruple that"), and the big television networks are also bullish on HDTV, already broadcasting in it to varying degrees. Still, HDTV has been the next big thing for a decade.

The last word: How many TV viewers will pay four figures to scrutinize Ray Romano's pores on Everybody Loves Raymond? If it's more than we think, Cuban could be on to something.