eRepublik as a massive online social strategy game.
It is a game, where you will find our virtual planet - with countries, people, economics, and wars. The game is driven by nationalism feeling which every body has. Every country is trying to to be the ruler of the world, and every citizen can devote to it - one can be a journalist, or a business man, a warrior or a president of a nation.
You should really check it out, its preety simple, yet addicting.