An online, web-based game, found at http://games.swirve.com/utopia/ - easily one of the more addictive online games around.
You get to run a province in a medieval kingdom, a choice of 8 races, various buildings to build, various military types based on race, wizard spells, thieves and thievery ... and you get dumped in a kingdom of 25 provinces, controlled by other human players with whom you must cooperate. There's 25 provinces per kingdom, 50 kingdoms per island and about 50 islands in the game, making for a LOT of players. real fun.