The Jim Bowens Disturbia Yahoo Group has free rules for the Gotterdammerung WWII-Horror game.
Based on DBA, De Bellus Mortuus is a set of free wargames rules for a fun zombie game. Author Chris Brantley writes:
This “just for fun” DBA adaptation is inspired by all those great zombie movies, ranging from the classic Night of the Living Dead to the comedic Sean of the Dead, as well as by the gamers who gather to hack and blast their way through legions of plastic zombies during local conventions. In this game, Players take sides, commanding either the forces of “The Living” or “The Undead.”
Slayer of Vampires is a set of free wargames rules for skirmishes set in the “Buffy” universe.
Strange Aeons is a skirmish wargame of Lovecraftian horror. You can get a Strange Aeons demo kit here, and the quick reference sheet for the second edition Strange Aeons here.
Dead Walk Again is a set of free wargames rules for skirmish games in the zombie apocalypse.