So...i pretty much like browsing art from time to time, and i've familiarized myself (and created accounts with) several art galleries. i figured it might be kind of neat to have a list of these galleries. feel free to add any that i've left off, as there are quite a few in the vast world of the internets.
http://www.deviantart.com/ (DA)
seriously, this is a HUGE site for everything arts. there's a lot of professional grade artwork here, but it isn't quality controled, so not everyone is awesome. the daily deviations are usually worth a peek though.
http://elfwood.lysator.liu.se/elfwood.pike (Elfwood, EW)
fantasy/sci-fi site mostly amateur artwork, but it's definately worth a look at the Moderator's Highlights.
http://artwanted.com/ (AW)
slightly smaller than DA, but i think it has more of a community feel. maybe that's because i'm not active in the forums, yet still have regular visitors who give very helpful critiques. many of the artists are older folks. quite a lot of professional work here, but again, not quality controlled. the fine art subgallery is definitely worth a look.
http://sheezyart.com/i'm not as familiar with this one--it just doesn't strike me as anything special, to be honest. the "masterpiece" thing seems to be worth a look. it seems much smaller, and maybe a bit more amateur friendly than other sites (DA and AW, eg), which have mostly pros.
www.epilogue.net
epilogue is another one i'm not as familiar with. epilogue is different from the other sites listed in that the artwork must be juried in--if the judges think it isn't good, it doesn't get in. while i've heard some complain of a somewhat elitist attitude among the artists at epilogue, i've never experienced it (because i'm not good enough to get in, lol).