Die2Nite is a game of survival set in a hostile world inhabited by the living dead.
The players (or citizens) are divided into groups and are allocated a small town where they must organise themselves each day in such a way as to survive as long as possible against these beings. The last remaining survivor will become the Hero of the town.
(from the site)
My own opinion? First cooperative multiplayer game I've ever actually liked and enjoyed. Despite the fact that you
will die in this game. Repeatedly. Quite fun with the right kind of players, though, and my previous town certainly had those.