Recently it was my son's 17th birthday. I decided it was about time I produced something finished from my time absorbing hobby, so I set about designing an amusing novelty present for him.
The original idea was to embed a device inside a sacrificial book [hardback] which would start to make a noise at a predetermined time [school break time] causing him to find it within his school bag, and upon opening it would display 'amusing' messages on an lcd.
For various reasons the project morphed into effectively a fat musical birthday card. I used an old 'learn Chinese' book with nearly every page glued together and hollowed out. I used a 16f468, a 2x16 lcd, piezo, microswitch and a 9v battery. Opening the book releases the microswitch which is in series with the battery. On powering up the pic displays 'happy birthday' etc. and plays 'happy birthday to you' on the piezo using timer1 interrupts.
Not much of a project, but it was fun and I think my son appreciated it [and I finished it!]. With a little more time it might have been a little more interactive, and the aesthetics might have been a little better, but I am encouraged and next time I might just do better...