Fire and Forget Games has released a downloadable PDF version of the rules for Faction Wars, the sci-fi skirmish game. The free 40-page PDF contains the basic rules of the game, sample squads for two factions, and a couple of scenarios to get you started.
Minifigz is a set of rules for combat with Lego figurines.
From Impact Games, Elfball is a set of fantasy “football” rules. It’s played on an oval field, so it’s not like “American Rules.”
MS Era is a set of free wargames rules for playing with those Mobile Suit Gundam figurines.