Urban Dead - A Massively Multi-Player Web-Based Zombie Apocalypse

"The city is dying. A month on from the first reported outbreak, military quarantine units have closed Malton's borders, and are moving in to eliminate the looters, to forcibly evacuate those civilians who still refuse to leave their homes.

The city is dying, and the urban dead are filling its streets.
Urban Dead is a browser-based, grid-mapped multi-player game where you play the survivor or victim of a zombie outbreak in a quarantined city centre."