(YouTube link)
I haven't spent this much time watching a clock move in ...a long time. Hans Andersson, who gave the Rubik's Cube-solving robot, built this clock called the Time Twister.
Time Twister consists of two LEGO Mindstorms bricks communicating via Bluetooth. The master brick keeps track of the time and handles the minute digits. The slave brick handles the hour digits and the second indicator.
Read more about it at the Tilted Twister site. Link -via Laughing Squid