[wundie]

Last FM (http://www.last.fm/) Has a great search tool where you can enter a band you like and it will suggest other new artists that you may enjoy listening to. Its pretty spot on and I've found a few new groups from the several times i've tried it. Its user driven so its virtual word of mouth.

[adamdoupe]

I particularly like the "neighbors" feature, which shows you people who have similar tastes as you. You can then see what they're listening to that you aren't. Also PureVolume (http://purevolume.com) is excellent for listening to independent music.