I Love Electric Sheep

Electric Sheep is the best screen-saver ever! At least once a day I marvel at it while passing my computer. I typically utter some unstoppable little word like "woah." I say it just like Keanu Reeves in Matrix, i've noticed. I mean, it's just that intense. *winks*

This was taken from ElectricSheep.org:

Electric Sheep is a free, open source screen saver created by Scott Draves. It's run by thousands of people all over the world, and can be installed on any ordinary PC or Mac. When these computers "sleep", the screen saver comes on and the computers communicate with each other by the internet to share the work of creating morphing abstract animations known as "sheep". The result is a collective "android dream", an homage to Philip K. Dick's novel Do Androids Dream of Electric Sheep?.

Anyone watching one of these computers may vote for their favorite animations using the keyboard. The more popular sheep live longer and reproduce according to a genetic algorithm with mutation and cross-over. Hence the flock evolves to please its global audience. You can also design your own sheep and submit them to the gene pool.