Flotilla is a set of free wargames rules for star ship fleets of twenty to thirty ships.
Rules: Science Fiction
Xenocide Firefight
Xenocide Firefight is a set of free wargames rule for science fiction games. Troops are organized in squads.
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.
Generic Legions – Big Battle Version
Generic Legions is a set of free wargames rules for science fiction warfare. This versions is, as the headline suggests, for big battles.