(FORTUNE Magazine) – Shopping online is a lot like taking Viagra, Propecia, Claritin, or one of today's other wonder drugs: It can dramatically improve your life--but expect some ugly side effects. In the plus column, the convenience of shopping over the Web can't be beat. Comparing prices and doing product research are easy; new technologies let you see stuff more clearly than ever, sample music before you buy it, maintain wish lists or idea files on a retailer's site, and even try clothes on a "virtual model" that has your body shape. Also, there are no parking hassles, no omnivorous sales associates, and no awkward moments at the Victoria's Secret panty bin while you rummage for your wife's next birthday gift.

On the other hand (and here's where the announcer warns you in a sunny voice that "some users experience side effects, including headache, nausea, and apoplexy"), online shopping is no more exempt from technological seizure than any other Internet-related experience. You can suffer countless hours of finger drumming, foot tapping, and head banging waiting for some sites to process your orders. Navigation can be difficult, searches fruitless, customer service nearly nonexistent. Or worse, you can stumble into technology so "revolutionary" that it promptly crashes your computer.

But with the sheer number of dollars poised to flood the online world (annual sales estimates range from $35 billion by 2002 to a pie-in-the-sky $400 billion), retailers are scrambling to iron out those glitches and create Websites that aren't just substitutes for stores but are actually better than them. In the past several months I've devoted countless hours to spending FORTUNE's money in the search for sites where online retailing is living up to that potential--or where it is at least moving in an interesting direction. Here, aside from an incredibly buff right index finger, is what I've come away with:

AMAZON.COM

Let's start at the benchmark--the first online retailer to emerge as a full-fledged cultural phenomenon. With 4.5 million customers to date, Amazon.com (www.amazon.com) is a leader in nearly every online retail category that counts--except profitability, but that's another story. The selection is legendary (as they never tire of telling us), with more than three million book, CD, and movie titles; prices are heavily discounted; and customer service, rarely a bragging point for online retailers, is consistently good.

Of course, those are features you'd expect of any retailer. But once you've bought something from Amazon, the advantages of digitized commerce start to become clear: Future purchases can be done literally with one click of the mouse; you can be updated by E-mail with news of favorite authors or subjects; and when it comes to tailoring the site to your interests, Amazon.com is one of the pioneers. The site's personalization technology will, for example, recommend books based on my transaction history and the ratings I've given to other titles. And if the technology is far from flawless (I said I liked one Anne Rice novel, and now Amazon thinks I'm a Gothic groupie), it's as effective as any clerk I've talked to at Barnes & Noble. Besides, the point is that it gives me leads, and from there I can use the interconnectedness of Amazon's site to track down other books, to read reviews, and to make discoveries on my own.

GARDEN.COM

Using Garden.com's onscreen Garden Planner template, I was on the verge of harvesting my first crop before I remembered that (a) I don't like gardening and (b) even if I did, I don't own any actual soil. But the design software was so compelling and the overall site so alluring that I was quickly E-planting rows of basil and checking the pH requirements of cilantro, broccoli, and garlic. I had to log off before I bought a pair of clogs and a big floppy hat.

Whether you care about gardening or not, Garden.com (www.garden.com) may be the best retail site on the Internet. It's a model for great Website design, with an intuitive understanding of how to make online shopping irresistible. By using photos, tips, and suggestions, it creates an environment like your favorite nursery, a place where all the salespeople are experts and nary a tomato worm rears its ugly head. It's shopping as a (horti)cultural experience, applying technology in the best possible ways. Simple things, like a gift registry and a notebook where you can store ideas or Web pages, turn the site into a tool rather than just a place to spend money. Regional planting guides and the garden design center let you reduce the cost of trial-and-error gardening. Finally, Garden.com is a showcase for highly sophisticated personalization software that runs laps around Amazon's rather ham-fisted techniques; it follows your "click stream" as you wander through its pages, tracking where and how you spend your time. Shades of Orwellian marketing? You bet. The future of E-retail? Get used to it.

LANDS' END

Lands' End's My Personal Model software (www.landsend.com) is either the future of online shopping or another example of technology trying too hard to do what's better done in real life. Using a program developed by Public Technologies Multimedia, My Personal Model enables women to build a three-dimensional model of themselves, then "try on" clothing combinations to see how they fit.

For the purpose of investigative journalism, I pretended I was Pamela Anderson, but my model came out built like Monica Lewinsky. Disappointed? Sure. But I was also impressed with how My Personal Model chose clothes that enhanced the more attractive parts of "my" body and downplayed the ones that recently made the papers. Just how well that digital effect translates into real life is the big variable, of course. But women who've used the technology love the privacy factor; developer PTM says they're way more candid with My Personal Model than they'd ever be with a salesclerk. (How PTM knows this is another question.)

ETOYS

You'd never know it from looking at its simple, almost boring home page, but eToys (www.etoys.com) is leading the charge of Small Soldiers, Mr. Potato Heads, and Teletubbies into the hottest new category of online shopping. While eToys doesn't score on aesthetics, it wins major points on efficiency, groupings, and searches. If you know what you want, it takes seconds to find it. And if you're, say, a clueless 45-year-old man shopping for a 7-year-old girl, the multiplatform search engines will still get you there pronto. Also, give props to eToys' almost Shaker starkness: Thanks to a lack of dancing icons, graphics-heavy pages, or RAM-greedy plug-ins, the pages load in the blink of an eye, never slowing or crashing your computer. That may sound fundamental, but you'd be amazed how many retailers ignore it.

N2K

Until spending the better part of a morning sampling some new music at N2K (www.n2k.com), I always figured the best thing about ordering music online was avoiding the sneers of some multiply pierced Gen X cashier as you fleshed out your Kenny Loggins collection. But I followed link after link, starting with Beck, on a journey of musical diversity that would have left Paul Simon winded. And I eventually came to the conclusion that "streaming audio," which allows you to listen to tunes on your PC, may be the best application of technology in the online shopping world. Especially when a site has over 400,000 albums to sample.

JUNGLEE, JANGO

It's a brilliant but elusive concept--an intelligent shopping agent that can search every nook and cranny of the Web for the lowest possible price and best terms for whatever you want to buy, be it a fan belt or a flamingo lawn ornament. Shopping agents--also called "bots"--do exist, but they're nowhere near their blue-sky image of a go-everywhere, do-everything device. Flaws and all, though, they're still worth exploring. Junglee (www.junglee.com) excels at ferreting out product reviews, manufacturers' sites, and other types of research, but it's anemic when digging up prices or comparing products. Jango (www.jango.excite.com) does a much better job of sniffing out low prices, but its research pales next to that of Junglee. Using both should even things out.

MERCEDES-BENZ

There isn't a whole lot of gee-whiz technology built into the Mercedes-Benz Website (www.usa.mercedes-benz.com), just the adrenaline rush of dropping $120,000 on a Benz while eating your morning bagel. In a frenzy of hypothetical consumerism, I signed on for the European delivery program and went all the way: a top-of-the-line SL600 coupe. (A paralegal's C230 and a senior partner's SL600 were only a click of the mouse--and $90,900--apart.)

Mercedes made the build-your-own process a little too easy, walking me through the color choices (I went for smoke silver exterior, java interior) and options (none, it's plenty loaded), and introducing me to the dealer who'd process the order. Okay, so it would have taken about four months for "my" car to be built, but the price--about $4,500 less than driving one off the lot in the States--includes shipping from Europe, two nights lodging near the factory in Sindelfingen, Germany, and two weeks zero-deductible insurance for cruising the autobahns worry-free.

CARPOINT

At the other end of the utilitarian-to-sybarite axis lies Carpoint (carpoint.msn.com). This is the Web at its research best, a four-star automobile site where you can check reliability, link to Blue Book prices, or fire up a new-car buying service. But the coolest thing on the site is the Surround Video Gallery. Click on any one of more than 50 vehicles, and if you have a superfast Internet connection and good computer karma, you can take a 360-degree tour of the inside or outside of the vehicle. If your machine's having a bad day, though, expect the worst the Internet can dish out: namely, plug-in incompatibility, which means the programmers tried to do too much with too little and overloaded your computer in the process. That irksome sort of side effect will send you packing from virtual stores faster than you can say dry mouth and migraine. The good news is that with the kind of money now being spent on smoothing out these technologies, relief can't be far off.