Shaun of the Dead is free card game based on the very funny movie of the same name.
zombie
Reanimation Zombie Survival Card Game
Reanimation is very highly rated at Board Game Geek. And it is free.
Dice of the Living Dead
Dice of The Living Dead is a free print-and-play zombie survival horror game.
Zombie Escape Rules
Zombie Escape is a Warhammer 40K modification for Imperial Guard versus Zombies