Nine Inch Nails is encouraging goofing around with its track The Hand That Feeds by releasing an Apple Garageband file containing its constituent parts, all ready for you to jigger about with as you see fit. The file offered is the actual one used to create the song, reformatted for size and tempo control.
"For quite some time I've been interested in the idea of allowing you the ability to tinker around with my tracks -- to create remixes, experiment, embellish or destroy what's there," -Trent

Read about it at Make Blog, get the remix file at the NIN homepage, and hear a few attempts for inspiration at Too Many Topics, Too Little Time.

Seen @ Joi Ito's Web Site