Hear it FIRST!
If you like to be the one who tells your friends about the coolest new tunes, you gotta check out this site.
PromoSquad.com has created an excellent online music research site. By collecting members who are willing to listen to clips of new music, then rate and comment on each song, PromoSquad has positioned itself as one of the first and best online music research sites.

A one minute clip is played three times and then the member is prompted to either play the clip again, or to rate the song via a check-box, and then leave a brief written opinion (this is a required field) before the system plays the next song. PromoSquad members are awarded 5 points for each song they rate. Points can be redeemed for some fairly decent prizes including CDs, software, electronics, and even the opportunity to have one of their favorite unsigned bands featured on the playlist. Additional points are awarded for participating in online polls, referring friends, suggesting new bands to feature, etc.

There are only a couple things I would change: Add the ability to completely bypass (or at least reduce the number of required plays) of songs that you immediately dislike, and provide the artist names for songs. I've heard at least 4 songs during my initial listening period that I would have liked to known more about -- but there doesn't seem to be a way to find this info on the site. So far my email requests for artist info have gone unanswered.

Overall, this is a very cool site and definitely worth a look... and listen. ;)
PromoSquad.com