Ross McFarlane’s 19th Century Square Brigadier rules are designed for late 19th Century wargames on a square gridded battlefield.
Charge of the Light Brigade is a set of free wargames rules by David Raybin for mid-19th century warfare. Raybin writes:
The rules (which have evolved over the last twenty years or so) were originally designed for conventions where players expected to be able to learn a game in under fifteen minutes and to start throwing dice almost immediately. Obviously, then, playability and fun are central to the rules. There is no strict ground or time scale. It is merely representational at best which, in truth, is all one can say about any wargame.
The prolific Tyneside Wargames Club has produced a set of free wargames rules for early 19th Century Skirmishes.
Edwardian Splendor is a set of free wargames rules for playing games with 54mm figures.
Ross MacFarlane offers a set of set of free wargames rules for the late 19th/ early 20th centuries called Sending MacDuff to the Front.