Instructables has an article on how to turn inexpensive hardware store caulk into casting material. I can see o-so-many applications for this one.
The Miniature Wargaming Editor
Three Plains 15mm Fantasy Wargaming
Three Plains is a free fantasy wargaming system. It also comes with free print-and-play figures.
Ravenfeast – Norse Saga Skirmish Rules
Ravenfeast is a set of free wargames rules for skirmishes in the Norse sagas.
Building African Terrain
Here’s a great illustrated post on building a spectacular African savanna battle board.
Brutality Skirmish Wargame
Brutality is a miniatures agnostic skirmish wargame set in a science fantasy realm. You can get a free version at the link.