18 Charlie has a photo tutorial on modeling security fences. These would look great on a modern, post-modern, or apocalyptic battlefield.
science fiction
Malifaux 2nd Edition Rules
The second edition Maifaux Rules are available free for the downloading.
The Stars Our Decimation: Voidstriker
The Stars Our Decimation: Voidstriker is a set of fleet oriented starship combat rules. They can be used as a board game, and with miniatures and hexless play.
Interspace Exploration and Exploitation Board Game
Interspace is an exploration and exploitation style board game free for the downloading.
Mobile Frame Zero Lego Rules
Mobile Frame Zero is a set of free wargames rules (although you can pay, too, if you like it and can get a printed version) for playing games using Lego and other construction toys. It is very well done.