Andy Watkins has these free simple skirmish rules for fighting miniature battles set in the French and Indian War. These rules belong to the "less is more" category.
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Fast Play Rules For The Seven Years War is a set of free wagames rules for mid 18th century games.
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.