Just ran across this post on CiboMahto’s blog detailing how to control an inexpensive analog clock mechanism with an Arduino.
The mechanical bit is quite simple. The clock functions in a similar fashion to a stepper motor, in the sense that you charge an electric coil to get the mechanical bit to move forward a precise amount. In this case, each firing moves the second hand one second position forward (and makes the familiar tick noise). To â€˜fireâ€™ the electric coil, you simply put a voltage across it. The only complicated bit is that you actually have to reverse this voltage to advance the clock to the next step.
Making a ‘totally crazy’ slow/fast/backwards clock could be a great way for newcomers to get their feet wet with microcontrollers. And for those feeling a bit less wacky, Info for accurate timely control is also provided on the project page.