Xenocide Firefight is a set of free wargames rule for science fiction games. Troops are organized in squads.
Miniatures Rules
Blaze of Glory Wild West Skirmish Rules
Blaze of Glory is a set of free wargames rules for Wild West skirmishes.
Warblocks Rules
Warblocks is a set of free wargames rules using Jenga blocks as troops.
Wastelands Post Apocalyptic Wargames Rules
The author writes:
Wasteland is a game of post-apocalyptic warfare between small bands of desperate fighters. You can play it as a skirmish war game using the character archetypes and weapon lists but it’s also designed to allow you to play fast-moving and memorable campaigns with two or more players.
Low Level Hell
Low Level Hell is a set of free wargames rules for helicopter actions in Vietnam.