Mophidus is offering free PDF core rules for their Fallout Wasteland Warfare game, based on the Fallout video game series. They also are have a free Fallout: Wasteland Warfare Getting Acclimated pdf with some basic scenarios and a guide to help start play. Other free offerings are Fallout Wasteland Warfare Dice and Ruler Info and high res player cards.
Miniatures Rules
Bushi Samurai Rules
Bushi is a set of free wargames rules for Samurai warfare. Each stand represents a band of warriors. Two bands equal 500 men.
Final Round WWII Skirmish Game
Final Round is a set of free wargames rules for WWII skirmishes.
Rules For 16th to 19th Century Naval Wargames
Erik Springelkamp offers a set of free wargames rules for 16th to 19th Century Naval Wargames.
Crimean War Rules
Natholeon’s Empires has a set of free wargames rules for the Crimean War.