NoiseTrade. Well, there is a little hitch as artists lose to the host 20% of fan donations and listeners can enjoy music in exchange for email address and zip code.
Nothing is worse for artists than obscurity, so bands might want to seriously consider sharing a few tunes with sites like the Free Music Archive (okay, so I'm partial!), Jamendo, Bandcamp, and NoiseTrade, among others. Make listeners love you.