Freight Wars is a tile placing game where you try to build a Victorian era transportation network of roads, rivers and railways.
What’s unique about this is that the print-and-play game actually consists of a program which randomly generates the tiles (For printing as a pdf), so that no two sets of tiles of Freight Wars are a like.
David Wareham offers a set of free wargames rules for Ancients battles. They use an alternate movement system and whole figure casualty removal.
Jim Gandy offers Marathon To Marne, a set of free wargames rules for games from ancient times to the widespread deployment of the machine gun.
Bonaparte is a set of free wargames rules for Napoleonic warfare. It’s in Portuguese, so your mileage may vary.
David Wareham offers a set of free wargames rules for the American War of Independence.