Empire of Liberty is a set of free wargames rules for playing the American Revolution. They fit on just two pages.
Direct PDF Download of Empire of Liberty. Author’s Page (I gave the direct download because the page is caught up in one of those infernal webring loops.)
The War Times Journal has a set of free Pre-Dreadnought Naval Warfare rules, designed for 1/3000 scale miniatures.
Bloodybacks is a set of free wargames rules for the American War of Independence by Stephen Jones.
Direct PDF Download of Bloodybacks American War of Independence Rules.
This set of free wargames rules for the American War of Independence is designed for 25mm/28mm rules at a scale of 1 figure = 10 – 20 men. Direct Download Word File: American War of Independence Rules
Quick War is a set of free wargames rules for WWII games using 1:144 miniatures. From the BGG author’s description:
This is a set of rules to play a WWII game with 1:144 miniatures. It doesn’t use a lot of look up tables, and is easy to learn. That’s why I call it “Quick War”. This set of rules uses no game board, instead units are moved by measurements in inches, and rulers are used also for firing weapons. I use different colors of felt to denote hills, forest, water, and roads. Units may be hidden and put on opportunity fire, or be activated to move and fire. There are rules for artillery and infantry as well. Infantry may be used as artillery spotters, or to attack other infantry or armor. There is also Infantry support which includes heavier weapons such as bazookas.