The prolific Tyneside Wargames Club has produced a set of free wargames rules for early 19th Century Skirmishes.
rules
Legends of the Feudal Times Skirmish Rules
Games Workshop’s Lord of the Rings rules set has turned out to be very flexible, spawning several commercial sets, such as Legends of the Old West and Legends of the High Seas and innumerable fan variants. Legends of the Feudal Times is a set of feudal skirmish rules originally published in the French language magazine Vae Victis. The English translation is here.
Battle Companies
Battle Companies is a fan created book of Lord of the Rings Battle Companies.
Reaper Minis Warlord Quick Play Rules
Reaper Minis offers a set of quick play rules called Warlord, designed for their figure lines.
Jutland: The Rules of the Game
Jutland: The Rules of the Game are a set of free wargames rules for large scale WWI Fleet Actions.