If you want to be all super-elite and OMFG IM SO INDIE IT HURTS, go through the reviews on
www.pitchforkmedia.com. You'll get a pretty good education in what's up and coming, as well as some good old stuff that you may not know about. That's the easy way though; I found out about most of the stuff I like by downloading stuff that I'd never heard of before, so that's another way to do it. Independent record label websites are also a good place to start. (There may be some more obscure bands that share a label with one you already like, for example).