This is fascinating to me -- musician Matthew Irvine Brown has compiled a set of 18 musical tracks, about an hour of music total, designed to be played in random order on the iPod shuffle. There was a lot of care and thought put into this as he designed the music to be atmospheric pieces. Even when shuffled, they'll work together no matter which order they're played. He also designed the sound of the music to fit with the iPod shuffle, hiding the glitch heard as the iPod switches tracks. As a final bonus, Matthew designed separate cover art for each track, so as a tune plays in iTunes, the cover art shows a very rough "animation."
You can see a two-minute sample of the work after the break, and download all of the music for free in a zip file if you want to give it a shot. Brown also says that the work is an example of "skip button as instrument," too. You can hit the skip button whenever you want to jump to the next track and change tempo or tone as you see fit. It's a cool composition meant specifically for Apple's smallest iPod.