Ancient Battlelines Clash is a set of free wargames rules from Shaun’s Wargaming With Miniatures Blog. Shaun writes:
Ancient Battlelines Clash is the ruleset I have written to be solo friendly, would play in less than 1 hour, preferably 20-30 minutes, on a 2’x2′ table and give a good game with what I want in historical feel.
Goodbyeee! is a set of free wargames rules for Great War skirmish actions.
Flanders Field is a set of free wargames rules for the first World War. It lets players conduct regimental to divisional level actions.
Land of the Lead has a set of one-page Napoleonics Rules. They’re designed for play with a “reinforced division” per side. Scroll down to the bottom of the page to find them.
Sulphur is a set of free wargames rules for post-apocalyptic skirmishes. There’s an accompanying 28mm line of figures.