I would recommend One Page Rules (https://onepagerules.com/
) as a solid collection of free miniatures rules for fantasy and 40k with full army lists. They also recently re-released their one off rule sets for green army men, car combat, deathball and others.
Also, similar to WOG, Ares naval combat Sails of Glory and Battlestar Galactica ship combat games have free rules. Although similar to Wings of Glory, there are lots of game pieces required to play that aren't included and would make playing it without the base game difficult.