The Electric Sheep
Electric Sheep is a free & open source screensaver created by Scott Draves. It is by far the most beautiful and captivating screensaver I've ever came across. It not only generates amazing images, but it does it "on the fly". When the computer "falls asleep" it starts communicating and collaborating with thousands of computers around the world morphing computer animations known as "sheep". The result of this constant transformation is what some call a collective "android dream", an reference to Philip K. Dick's novel "Do Androids Dream of Electric Sheep?".