Mike Szczys from Hack a Day built a Ping Pong LED Clock, Mike did some nice woodworking on the box to give the clock parts a nice case to shine from. A AVR microcontroller the heart of the clock and a Maxim DS3232 and a coin cell are used to keep track of time. LEDs are inserted through a peg board and ping pong balls with holes cut in the base are placed over them to diffuse the light. The control buttons are a nice touch since they are actually pieces of wood that protrude through the case of the clock. Nice thing about the design is that since 74hc595 serial to parallel chips are used the number of controlled LEDs could easily grow to whatever you need.
