the one i'm most active on is recolor.me
before that i was on gaia for a while, but i left after the zOMG crisis
i have accounts on windlyn, syndrone, caedon, subeta, roliana, goatlings, and probably a few others i've forgotten. i visit some from time to time if i remember to (windlyn is my fav of the bunch <3)
i used to be on tinier.me and ernya, too, before they shut down, which sucks because i really enjoyed those sites