Steam Iron and Tin is a set of 15mm ACW naval rules that was distributed to people who attended the 1985 Origins Convention in Baltimore (I was at that convention!).
Miniatures Rules
The Thin Red Line Napoleonics Rules
The Thin Red Line is a set of free wargames rules for Napoleonics warfare based on the Flames of War Rules.
A Marvelous Victory
The Armchair General offers a set of free wargames rules for 25mm / 28mm Napoleonics called A Marvelous Victory
Minden Rose Seven Years War Rules
Minden Rose is a set of free wargames rules for playing Seven Years War battles. It is designed for 25mm or 15mm figures.
Warzone Rule Sets
Here’s a page with downloads for all the Warzone Rules sets, from First Edition through Ultimate Warzone including the faction books, board games and Fictional Reality rules.