Not my idea I'm afraid but also check out the June 99 (yes - it
came out last week!) edition of the UK magazine Everyday
Practical Electronics.

It has a PIC based sundial. When the shadow drops over one of the
hour markers the hours pip and the tune 'You are My Sunshine'
plays. Looks like a few other fun features also. Probably not up on
their website yet but their normal practice is to make the source
code available for FTP.

Brian
Brian E Jones
Centre for Java Technology
IBM HURSLEY