BME is very cool, as the others have said... I also like these personal sites, which have a LOT of beautiful images to peruse.

http://www.anilgupta.com/
http://www.vyvyn.com/gallery.htm
http://www.tattoocitysf.com/artists.html
http://idlehandsf.com/section/37011.html (Aaron from this shop is my current artist )