Urban Dead was fun back when I played it. Used to be on the forums a lot and organize curing centres or safe zones.
Dominate Game. Great online risk game with elo system. You could play the default maps in the browser but thier client let you play tons of customer player made maps. Sadly this one got taken down a long time ago, is has a spiritual successor as Dominate 12.
Supremacy 1914. Only played 2 matches of this game, but do to its nature it was over the course of 6 months or so. I believe they have a download client now and the game is also on Steam now.