Check out this awesome cool Gear Clock my friend Alan from HackedGadgets made! The Gear Clock features CNC, laser-cut gears coupled with a PIC 16f628A microcontroller and a stepper motor. Brilliant, I WANT ONE!
The heart of the clock is a PIC 16f628A microcontroller (PDF). This microcontroller has an internal oscillator however an external 20MHz crystal oscillator is being used since it will have to accurately keep track of time for weeks and months. The microcontroller is interfaced to two buttons and one motor.