Limor of ladyada.net, an engineer from MIT, put out a HOW-TO make an MP3 player from a box of Altoids.

The Minty MP3 player can be built from parts that are sold at Ye Olde Traditional electronics distributor (digikey/mouser/newark). Half of the parts can be sampled for free, for a minimal total cost of $25 for parts, and $25 for a PCB. And the case is soooo Minty!