It's gotta be the coolest screensaver ever, electric sheep is a continually evolving flame fractal animated screen saver, where your idle cpu cycles are used as part of a distributed computing network to render frames towards the next phase in the evolution (known as sheep).
The name is a little strange, but if you consider idle cpu cycles as dreams, and consider the novel "Do Andriods Dream of Electric Sheep", you'll get the idea. (If you're more into movies than books, "Blade Runner" is for you).
It is a little slow to pick up the first "sheep", but that appears to be a bandwidth problem on their central server. Perhaps they should also distribute the sheep downloads among mirrors, or even peers (Bit Torrent style)?
Anyway, the coolest thing about this screen saver is that is subtly changing the whole time; I have it running on a spare computer next to me and its fascinating.