Several of them are still around. At least half a dozen are trying to prove what many doubt--that there's a market for a virtual desktop with built-in applications and widgets, plus communications and collaboration tools, all served via the browser.
Among those CNET News reached, Glide OS is now the biggest, with about 1 million users, followed by Desktoptwo with 200,000 users, Ghost with 180,000 users, Icloud with 170,000 users, Startforce with 70,000 users, and Cloudo with 30,000 users.
Though the numbers aren't overwhelming, they indicate at least some interest.
On the other hand, a couple of Webtops we've reported on, Jooce and AjaxWindows, appear to be out of commission, or at least their Web sites are. And one of the best known, You OS, called it quits last summer.
Yet those still standing believe their time is now slowly coming.
"What we've noticed in the last four months is that with virtually no media coverage, we've had a steady upsurge and it's purely viral," said Donald Leka, founder and CEO of TransMedia, which runs the Glide OS.
But Ray Valdes, research director at Gartner Research, is skeptical.
"I have not seen growth or traction among the Webtop companies over the past year," Valdes said. "From a long-term perspective, I don't see any change to current market trends, which are that Webtop ventures are not gaining market traction."
Still, investors are watching the Webtop market closely.
"We have a tremendous interest from venture capital," Leka said, underlining that TransMedia so far is wholly angel-funded. "Repeatedly we get calls on a weekly basis."
And Daniel Arthursson, CEO and founder of Icloud developer Xcerion, said his company just raised new capital from new and existing investors, including Northzone Ventures, which invested $10 million in 2007.
Though the Webtops are similar, each has its own approach. Ghost, which launched Tuesday, connects to all major Web-based applications such as Google Docs and Zoho, instead of offering its own applications inside the Webtop.
Glide, launched in 2005, now offers native clients for several operating systems, which helps improve performance, and will soon do the same for mobile phones. It's also planning features such as a Twitter-like service called Engage and tailored packages for health care professionals and educational institutions.
Desktoptwo was launched by American-Mexican Sapotek in 2006. It's Flash-based in the front end, but can also run outside of the browser in Adobe's AIR runtime environment.
Icloud launched its public beta in April after eight years of development. It sticks to a no-download approach and has planned to develop Netbooks with a Linux kernel and a browser on top that opens the Webtop in full-screen mode. The idea is similar to the recently announced Google Chrome OS, which is not a Webtop as some might think, but a Linux Kernel with the Chrome browser on top for easy access to Web applications from various devices.
Icloud also claims to be one of the few software systems to have a complete separation between data, logic code, and user interface--also known as Model-view-controller, or MVC. Among other things, this lets a user drag a window off the screen on one side; it then shows up on another user's screen from the other side.
Startforce, which launched in 2007 and is characterized by a Windows "look and feel," also is handling Office documents through software from Chinese Kingsoft. It also has an enterprise version for corporations with paid support.
Cloudo is still in developer beta, so the public hasn't yet had the opportunity to test it.
There is also the Barcelona-based EyeOS, an open-source project that exists both as a public Webtop and as open-source software that anyone can download and install on a server. A similar platform is OpenLaszlo, though it doesn't offer a Webtop for end users.
Adding to the competition between the Webtop companies are giants such as Google and Microsoft.
Leka pointed out that applications in Webtops such as Glide OS are developed in-house to ensure seamless integration, while still offering cross-platform computing. Google's Web applications are the result of the company's own development and acquisitions, not giving the same seamless user experience.
But this is not necessarily a show-stopper for Google.
"There is often a trade-off between homogeneous architecture, on the one hand, versus agility, scale, and depth, on the other," said Valdes at Gartner Research.