Empire of Liberty is a set of free wargames rules for playing the American Revolution. They fit on just two pages.
Here's a tutorial on painting the Perry AWI Continentals.
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
Braid and Cockade is a set of free wargames rules for game set in the 1750 - 1850 era.
Scott Mingus offers a Johnny Reb variant for playing the American War of Independence.