How about an automatically set clock? You can get seven segment displays very cheaply, so with those and a PIC you could make a clock. Then you could add a receiver module to receive DCF77, MSF60 etc (depending on where in the world you are) which would continually update the clock with very high accuracy. You can choose to make the receiver part yourself or buy a cheap receiver module already built.
You would learn a lot of different technologies for quite a small outlay.