Strange Aeons is a commerical rules set, but if you already own it, you may be interested in these free modifications for playing in an 18th Century setting.
Miniatures Rules
A Splendid Victory ECW Rules
A Splendid Victory is a set of free wargames rules for the English Civil War. They’re designed for 28mm figures, but the basing system is flexible.
Pigs and Glory: The Viking Sagas
Pigs and Glory is a set of free wargames rules for Viking Saga Campaigns. It is designed to give some context to period battles.
1862 Campaign Rules
1862 is a set of American Civil War Campaign Rules designed for Johnny Reb, but which could be used with any miniatures rules set.
Quick Play Low Intensity Warfare Campaign Rules
Quick Play Low Intensity is a set of free wargames rules for playing campaigns set in Vietnam or similar conflicts.