Everyone running Vista Ultimate saw the same thing I did this morning: the limited preview of Vista’s DreamScene which we saw demonstrated at CES. This is essentially an active desktop background that can be animated. I called this a "limited" preview because there’s currently only one scene to view, but I did a little digging and found a free extension to it from Stardock called DeskScapes.
DeskScapes provides additional scenes for installation and usage; there’s just a few at the moment, but I’d expect more to follow. If you want to create your own DeskScapes, there’s a download for that too: you’ll create .dream files for DeskScapes to show as an animated background. I’m using a rather psychedelic one that moves at the moment, but I’ll be checking out the Nebula and others soon. You will need to have an Aero-capable graphics card to run Vista’s DreamScene and the DeskScapes (which requires Vista Ultimate), so keep that in mind.