I got a link to this from MegaTokyo, and couldnb't stop playing it for a long while.... AdventureQuest (www.battleon.com) is a nice little RPG that's hosting online, but is not Massively Multiplayable, still tons of fun though, and is being updated once every week. Good quests, and leveling up is fun, it is free, though you can pay a one-time fee of $ 12 for some extra features.

I found it to be good fun, try it out sometime.