Anyone reading my HP fics will probably know more about the state of the fandom than I do at present. However, on the offchance that some of you Potter fans wander into GW and get sucked in the way I did, here are the best places to start looking for fics.
G.W.Yaoi
Lev's Lair - now closed.
Aenai-Ai
Sweetly Sour
Casey's Quiet Space