Like above, I've gone to Pitchfork for about 5 years now, nearly everyday unless I'm away from my computer. I also frequent
Indieworkshop and
Tinymixtapes, also good sorces of small-label stuff.
Also, I find it really useful to just look on the sides of the CD's you own, figure out the label and then go to their site and poke around, see what other artists are on that label. Most will have mp3 samples, etc. Now, this really only works if you're dealing with smaller labels...I mean, go to Sony Records and you'll be searching through hundreds of artists. But if you like someone and they're on a label you haven't heard much about, odds are, you might like some of the other bands they've signed.
And, for a personal plug
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
, I've started a blog that covers mostly music, but every now and again will have art, photography, books, etc. Not a review site as I don't fancy myself a critic, but just my thoughts on albums that I'm digging at the time, mostly to keep my friends in the loop:
http://mixedmediaproject.blogspot.com
I just started it about two weeks, so the posts are limited, but keep checking back–it will certainly grow.