here it is :) (http://kevan.org/proce55ing/zombies/)

Old. Here are the newer versions:
Zombie 3 (same as 2, but you can nuke the zombies. (http://www.hardcorepawn.com/zombie3/index2.php)

Zombie 4(FPS) (http://www.hardcorepawn.com/zombie4/)

There's also a Zombie 1 out there, which is the same as Zombie 2 exept zombies can't dig through walls.

All by the same author.