Ironclad Draughts is a set of one-page rules for playing out battles between ironclads.
rules
Air War 1917
Air War 1917 is a barebones — and free — version of Wessex Games’ AirWar: 1918 biplane combat rules.
Forge of War Science Fiction Rules
Forge of War is a set of free science fiction skirmish rules from Craig Cartmell. He writes that they were born of frustration with the Warhammer 40K rules from Games Workshop.
Elan Deluxe Napoleonic Rules
Elan Deluxe is a set of free rules for playing Napoleonic wargames. Once published professionally, it now is available online. This is a very well done, and interesting set of rules. The nominal scale is 1-50, with units representing battalions and regiments.
Bloody Big World War II Battles
Bloody Big World War II Battles is a set of free wargames rules for large scale WWII battles. Each base in the game represents a battalion or regiment. The ground scale is either 3” or 6” to the kilometer. Time scale is 1turn = 2 or 1hrs. One model represents 30 or 10 vehicles / guns or half a battalion or company of infantry