http://www.travian.com/
It is kind of a simplified version of a Civ style game that plays in the browser, its fun and hey it works in a browser. No ads, just full on game wars
server 5 - NE region
Once your city is established, takes very little from your day to kill and pillage everyone else (game runs on real world time) and makes a great reason to have yet one more tab open.
