Thanks to Jason I have discovered the wonderful world of Urban Dead is a massively multi-player web-based zombie apocalypse game. Create a character (human or zombie) and start to do battle with others online for control of the city. No flash, ActiveX, or Java required. Currently I have two characters; brockers and S1ider but I think one of them will become a Zombie pretty soon based on the fact that I left him sitting outside on the street because I didn’t entirely understand the daily usage limits.
Urban Dead also pointed me to another (admittedly less advanced) web-based MMPOG called Vampires! The Dark Alleyway. brockers can also be found in Vampires.