GarageSpin

If you haven't checked out SongFight yet, you should.  It's basically an online, weekly songwriting competition where bands submit brand new songs written and recorded in response to song titles proposed by the site's administrators. 

It's an absolute blast to see what people come up with in only a week's time.  One current song title is "Influential Film."  19 mp3s of songs were submitted, ranging from rock to mashups of film quotes, to pure electronica soundscapes, etc, varying widely in quality and style.  (I ended up voting for some dude named Jordan Seavers)  Everything's downloadable, and available as a podcast.

There's a ton of other stuff going on at the site; the community is pretty active.  Check it out, vote for a song, or submit your own track.

UPDATE:  I just noticed that the guy I voted for, Jordan, has won 6 of the 9 Songfights he's submitted to.  WOW.  Talk about a great way to identify great talent...  Labels and music publishers should take notice...