(Business 2.0) - It's been a long time--all the way back to the dawn of desktop computing in the early 1980s--since software coders have had as much fun as they're having right now. But today, browser-based applications are where the action is. A killer app no longer requires hundreds of drones slaving away on millions of lines of code. Three or four engineers and a steady supply of Red Bull is all it takes to rapidly turn a midnight brainstorm into a website so hot it melts the servers.

What has changed is the way today's Web-based apps can run almost as seamlessly as programs used on the desktop, with embedded audio, video, and drag-and-drop ease of use. Behind this Web-desktop fusion are technologies like Ajax (asynchronous JavaScript and XML), Macromedia's Flash, and Ruby on Rails. We'll spare you the technical details; suffice it to say that these technologies are giving rise to a new webtop that may one day replace your suite of desktop applications.

Start with Writely, a free online word processor that anyone who knows how to use Microsoft Word will figure out in a few clicks. Then add Zimbra, which is taking a swipe at Microsoft Outlook with an online e-mail application that has all the latest Ajax tricks built in. Glide a mouse over a message that includes a date, and your calendar for that day pops up. Move it over a website address, and an image of the page appears. For an online spreadsheet, try Tracker, the latest release from JotSpot (better known for its group-editing "wiki" software). Tracker becomes an interactive website open to viewing or changing by the people you invite. Users also will soon be able to subscribe to a particular spreadsheet row (say, "Sales in China") via an RSS feed. All of these programs link to myriad open APIs--advanced program interfaces that serve as building blocks for new applications--and data on the Web from Amazon (Research), Google (Research), and others. Thus can the information on your desktop be fused with the entire Web through a powerful and increasingly invisible bridge between the two.

Google, Microsof (Research)t, and Yahoo (Research) are energetically trying to crash this party. Microsoft recently launched Windows Live, a personal online command center for e-mail, RSS feeds, and other content, and is preparing to follow up soon with Office Live, a website-hosting and online project-management service that taps into the existing Office desktop programs.

THE WEBTOP

Company: JotSpot (Palo Alto)

What It Is: Wikis and online spreadsheets

Next Net Bona Fides: A pioneer of Web collaboration apps, a.k.a. wikis, it has unveiled its new Tracker application, which provides a powerful, highly collaborative online spreadsheet.

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Company: 30Boxes (San Francisco)

What it is: Online calendar

Next Net Bona Fides: This Web-based software allows families and groups to create private social networks, organize events, track schedules, and share photos; it may soon allow you to save phone numbers as hyperlinks and make calls by simply clicking on a link.

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Company: 37Signals (Chicago)

What It Is: Online project management

Next Net Bona Fides: Its Basecamp app, elegant and inexpensive, enables the creation, sharing, and tracking of to-do lists, files, performance milestones, and other key project metrics; related app Backpack, recently released, is a powerful online organizer for individuals.

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Company: Writely (Portola Valley, CA)

What It Is: Online word processing

Next Net Bona Fides: It enables online creation of documents, opens them to collaboration by anyone anywhere, and simplifies publishing the end result on a website as a blog entry.

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Company: Zimbra (San Mateo, CA)

What It Is: Online e-mail

Next Net Bona Fides: Taking aim at Microsoft Outlook, its Ajax-based application can, among other things, bring up your calendar for any date your mouse encounters, launch Skype for any phone number, or retrieve a Google map for any address.

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INCUMBENT TO WATCH

Microsoft. By rolling out Windows Live, Office Live, and other Next Net-centric software, it hopes to grab a dominant--if not monopolistic--share of the webtop, which Bill Gates regards as a crucial strategic priority.