Yod'm 3D is a virtual desktop manager that allows you to have 4 different desktops arranged on a 3D cube. Holding down CTRL+SHIFT and using the left or right arrow keys rotate the cube showing the virtual desktops. Alternatively, you can click and drag your mouse to switch desktops.
* Because of the capture software I used, the video is very choppy. Normally, the cube spins very smoothly.
Download this free desktop manager from Chris' Soft.
Update: Yod'm 3D Desktop was sold to a commercial developer and is now called DeskSpace. Additionally, DeskSpace is no longer free but you can find a copy of the old freeware version here.