Utopia is a massive multiplayer internet-based strategy game.
Its a turn-based, text-based strategy game. You join a kingdom with 23 or so other players and battle with other players in other kingdoms to expand your land and your worth. You train soldiers, wizards and thieves, and build various buildings to improve and grow your province.
Turns are taken once an hour (building, training, research etc), but you can attack/steal/etc anytime. You really only need to devote a few minutes at a time to the game to participate, thanks to the turn structure.
Wikipedia Entry
One thing to note, a game cycle lasts 3 or 4 months (an 'Age'), and then all kingdoms are wiped and everyone starts back from square one. This next such 'Age' starts like next Tuesday or Wednesday.