A friend is developing an interesting project. It is some kind of persistent, multi-player Civilization game. It is named "Alter Ages". You can sign up for the beta right now:
Depending on the size of the map, a single game could take up to a few hundred players. It can be played from your web-browser, but don't be mistaken, it is not like those old web-based strategy games. It feels more like a desktop game.
Beta will probably start in the summer. They are still working on it, mainly the graphics, but already looks quite interesting.