My friend Quinn described Songfight as “a Worth1000 for songs.” The organizers post titles of notional songs, and then the participants in the site compete to write, perform and record the best possible song to fit the title, with the winner determined by popular vote.
(Thanks, Quinn!)
Update: Tycho sez, “RemixFight is even cooler.
Artists take the same WAV samples and make wildly different and
innovative creations.”