Bill Molyneaux offers a set of free wargames rules for fighting the Zulu war.
Sand Pebbles Boxer Rebellion Edition is a set of free wargames rules from Bill Molyneaux.
Battle for the Bliss Farm is a scenario and set of free wargames rules for the American Civil War.
Gettysburg Gamers offer a set of free wargames rules for Napoleonic warfare.
Ross Macfarlane offers A Gathering of Hosts, an ancients wargame. Ross writes:
This is a set of simple rules for playing wargames with toy soldiers depicting ancient warriors. It is not a detailed, simulation of low level ancient tactics or high level ancient command, nor is it intended to be a clever vehicle for challenging competition style games. It is, hopefully, a relaxed game where the gamer can focus on his over all plan, not minor tactical details while getting enough flavour to feel right at a high level.