Neutron York 3000 is a set of free wargames rules for skirmish games in a post apocalyptic future.
Rules: Post Apocalypse
Axles and Allows Car Combat Game
Axles and Alloys is a set of free wargames rules for futuristic vehicular combat.
Fallout Warfare
Fallout Warfare is a set of miniatures rules for playing games set in the universe of the acclaimed Fallout computer game.
Nuclear Renaissance Rules
Ramshackle Games offers Nuclear Renaissance, a set of free, downloadable rules for playing skirmishes set in a post nuclear holocaust. There’s both a full color, and a printer friendly set.
The game puts me in mind of one of the favorites from my childhood — Gamma World. You had to love that chart for checking out various objects you discovered.
New Vegas Fallout Skirmish Game
New Vegas is a set of free wargames rules designed with playing a Fallout style post apocalypse game in mind.