Castles, Cogs & Chevauchées is a set of campaign style rules for skirmish level combat using the Knights and Knaves skirmish rules.
Knights and Knaves rules at the same link
Miniatures Rules
Coastal Warfare Rules
Richard Bradley has a set of WWII Coastal Warfare Rules. This is a period I’ve always wanted to play.
Greater Space Battles
Greater Space Battles is a set of solo rules for space battles using miniatures from Solipsist Games.
Familia Gladiatoria Gladiator Rules
Familia Gladiatoria is a set of free wargames rules for gladiator campaigns.
Iron and Steam Rules
Iron and Steam is a set of free wargames rules for pre-dreadnought Victorian naval actions.
Iron and Steam is a set of miniatures rules for naval combat of the American Civil War. The rules feature a gun-by-gun combat resolution, written orders and simultaneous movement. Traditionally played with 1/600 scale models the combat scale is closer to 1/2400 scale, though the game is generally model scale agnostic. Also included are over 100 pre-filled ship record sheets, turning radii and arc-of-fire templates as well as a 2 page QRS to facilitate fire resolution.