An archive of chiptunes ripped from keygen software, cracks, game trainers, demos, and intros. Sometimes this music is better than that of the game itself.
Stefan Ossowskis Schatztruhe has just uploaded a four disk archive of MODs, S3Ms, XMs, and other tracker music files to archive.org. If you're into chiptunes (Amiga MODs, in particular) this is at least a year's worth of music to listen to.