My wife recently told me about Pandora, a music site that quite frankly is one of the most interesting sites I've seen in a long time. With Pandora you'll find all kinds of incredible new music, from artists you know and artists that are very similar to the ones you like.
Simply go to their site, type in an artist or song you like, and Pandora streams you songs and artists that are similar. It's like having a smart Itunes playlist that gives you suggestions customized to your personal tastes. Not only have I found some incredible new bands that I like, but I also have heard many of the "B" songs from artists I like that never got radio play and that I never knew existed.
Now if I could just use Pandora on a portable player or on my radio in my car. :-)
