Electric Sheep is a free open source code screensaver which is run by thousands of computers all around the world.
When your screensavers start running, it creates an electric sheep which is sent to a central server were it will be mixed with other electric sheeps and they'll create a robotic dream.
Furthermore, you can rate the electric sheeps, and the more votes an electric sheep has, the more times it appears in different computers, If you create some sheeps and they become popular, they will interbreed with the rest of the flock and produce children. By mutating and crossing the genomes, variations of your sheep will appear and themselves evolve.
If you like Blade Runner, enjoy this amazing screensaver.