I'd like to mention SecondLife again (somebody mentioned it in this thread a ways back)... the client (for windows, mac AND linux) has been open-sourced and the world is growing hugely... it is free to play. You can do anything there and there is SO MUCH to explore. You pay only if you want to own land or run a business or purchase currency. With it's own economy, combat system, 3D building tool, etc.. I see it as a perfect role-players paradise. Everybody that enjoys planeshift should check out secondlife.com. Come to think of it, with a bit of effort and money, planeshift in it's entirety could be replicated in secondlife!