We've already seen Web-based desktops from the likes of Laszlo with its Webtop (see video) and from Sapotek with its Desktoptwo (see video) -- both of which pursue different models (the former, you must host behind your firewall; the latter is hosted multitenant style by Sapotek) and both of which encourage third-party developers to join the ecosystem with their own applications for the two platforms. And, while we have seen several outfits offer a portfolio of Web-based desktop functionality in decidedly non-desktop like user experiences (eg: Google Apps), none of the big guns have weighed-in with a browser-based experience that mimics the user experience found in today's desktop operating systems like Windows, Mac, and Linux. Perhaps until now.
While I'm still waiting to hear back from saleforce.com for an explanation of what's up, here are some screenshots of a user experience that takes the tabs that you normally find along the top of salesforce.com's standard Web-based user interface, and converts them into icons and menu items in what is clearly a browser-based desktop-like user interface (continued below....).
On salesforce.com's Dev Net wiki is a page that describes the user interface (along with links to the functional version that I got the screen shots from ) as the VisualForce Desktop. As a proof of concept, the VisualForce Desktop shows how any functionality that's inherently available through salesforce.com's developer environments (including the native functionality built into salesforce.com or third party applications that are built in the Apex programming language and that run on saleforce's multitenant utility-delivered virtual machine) can be ported to run on a desktop like browser-based user interface.
I'm trying to imagine what's not possible by virtue of this marriage and can't think of anything. Although salesforce.com is primarily used for salesforce automation and customer relationship management applications, its platform is clearly powerful enough to support any data driven application (in other words, applications that can benefit from salesforce.com's database functionality). And, given that it's a mashable platform, there's no reason that this saleforce hosted Web-top can't be stretched (under the hood) to pull in other third party functionality (through APIs) that isn't natively available from salesforce (eg: mapping).
When an if we hear more, we'll let you know.