Junior General has a simple set of Medieval Castle siege rules. The site also has links to appropriate paper figures, castle models and siege equipment.
Miniatures Rules
One Page Little Wars
From the One Page Rules guys comes a game based on HG Wells’ seminal Little Wars: One Page Little Wars
Modern – Futuristic Cargo Container Paper Models
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 Space Battles Game
Orion’s Gate is a one-page space battles game.
Napnuts Peninsular Campaign Rules
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.