David Heading offers a set of Renaissance Naval Rules.
The Miniature Wargaming Editor
Dragon Slayers RPG
Dragon Slayers is a playest version of an upcoming free role playing game. The author writes:
Dragon Slayers RPG looks like Savage Worlds but plays like D&D 5e. The goal is to have D&D-style adventuring without the fiddly bits. GMing is easy and the game is great for new players and one-shots. It features step-die mechanics and has inherited a few dirty hippie quirks (abstract equipment, 13th Age style backgrounds). Magic is low-ish powered and mages cast with spell points.
Dusty Trails Gunfight Game
Dusty Trails is a set of free rules for wild west gunfights.
WWII Simples Miniatures Rules
WWII Simples is a one-page set of free wargames rules for WWII Skirmish games.