From the One Page Rules guys comes a game based on HG Wells’ seminal Little Wars: One Page Little Wars
Marcos at Topsolitario offers a set of free paper models of cargo containers for your modern and futuristic miniatures games. They are quite lovely. There’s even a video showing how to build them.
Orion’s Gate is a one-page space battles game.
The Napnuts site has a set of rules for conducting a Napoleonic Peninsular campaign. The Peninsular Campaign makes for a good campaign because of its relatively limited scope.
Double Tap is a set of free wargames rules for games involving special operations forces in the near future. The rules are just one page, but look as though they are anything but simplistic, as they use a reaction system.