Tim’s Wargaming Blog has a photo tutorial on making “36 Miles of Barbed Wire.”
Lightning War is a set of company level rules for World War II> Emphasis is on training and troop types.
Crunch Waffle Games offers Extra Terrae Crepusculum, a free fantasy skirmish wargame designed to allow you to use miniatures from any other game system or line. Crunch Waffle is of course, a miniatures company and surely hopes that this will spur sales. It’s a great idea. I’ve long thought that miniatures companies should give away their rules to sell the miniatures — sort of the Gillette theory of game sales: give away the handle and charge them for the blades.
Steel Rain is a set of rules for 1/300 scale science fiction miniatures.
Andy Watkins offers a set of free wargames rules called Brigade Commander, for games set in Cold War Germany. Given the equipment used, I suppose it also would be useful for gaming some other scenarios in which the combatants have old NATO and Warsaw Pace equipment.