Um, well, the ones I know of are: Fairyland, Runescape, Aspereta(sp?), and...damn, I forgot the last one. I think Planeshift is one, though I'm not completely sure. Tibia might be.

It's hard to find good ones, because most of those you either have to pay (duh) or you download, and then after a month or so, then they charge. Nobody seems to want to spread the love, freely.