Archipelago of Gold is a set of free wargames rules for use with the constructable, collectable Pirates of the Spanish Main ships from WizKids. From the BGG description:
These rules use the Pirates of the Spanish Main and a hex map to allow you to explore wild islands for gold, build large fleets, settlements, cities, forts, and train your crews to become superior gun crews. Get more gold back to your settlement, and you can build more than your opponents.
Necropolis is described as a:
Necropolis is a home-grown horror skirmish miniatures game that pits a small group of desperate heroes against a variety of horror enemies from zombies to vampires, werewolves, serial killers and anything else a fevered mind can come up with
Taking The Bull By The Horns is a set of free wargames rules for Zulu War skirmishes in 1/300 scale.
David Wareham offers a set of free wargames rules for the 19th Century along with army lists. Scale is 1 figure to 30 men.
La Petit Guerre is a set of free wargames rules for small scale actions in North America in the 17th – 19th century.