the only online rpg's i know of are the message board kind where you write out a story type thing...yes, i belong to some of them when im REALLY bored
Well there is the Edge of Darkness which is a MUD (multi-user dungeon). It is a text game and can be played virtually anywhere on any comptuer. It is played using telnet or a mud client (ZMUD is the most popular one). I don't have the website but search google for it and it will come up (if you're interested).
Try Shatted Earth. It's not complete yet. It's in alpha, not beta. www.shatteredearth.net I thought it was a ko0l game.