One of the most useful and interesting features on Linux systems is the ability to switch between multiple desktops, an option that is still missing on Windows, even in the latest builds.
Most Linux distributions today are able to perform some sort of switching between desktops. Users can even create more or delete them. On Ubuntu, for example, you can even see all four of them at once and move applications naturally from one to another.
An Ubuntu user has posted a very nice screenshot with his desktop in which he is showing the multi-desktop feature. He has a browser, a simple desktop, Left 4 Dead 2, and Windows 7 in VirtualBox, all running at the same time.
The beauty of it is that it doesn't even require a lot of resources. Given the fact that even Mac OS X has a form of multiple desktops, it's going to be interesting to see how long it will take Microsoft to have a similar feature on its operating system.