Lionhead Studios announced that there will be some downloadable content coming out early December. It'll add some new items and weapons and a new island. It'll cost you a good 800 MS points for it though, so I think I'll hold off on that til the price drops a bit.

Let's see here. On my list of MMOs that I play, There's WoW of course and I believe someone already mentioned Warhammer Online. Both are really great Pay to plays. But then you have Guild Wars that is a one shot buy. You just pay for the game itself. It gives you a CD key and you're set to play without paying. I believe the initial charge is 20 bucks per expansion, in which there is 4. 3 of them are just stand alone and can be played separately, and the 4th you HAVE to have one of the three. There's a really neat one coming out soon called Aion, which is done by NCSoft, the same people that did Guild Wars.
There's also a good Free to Play called Atlantica Online. It's a Turned Based MMORPG, but it's done really well. I was a bit skeptic about it. There's also EVE online, but that ones going down the drain. No one really plays that anymore. The top ones to play with the most people are WoW, Warhammer Online, and Guild Wars. Hope that helps. If you have any questions, just send me a message and I'll be glad to answer them.