Stephan Hess has written Chariotmaster, a set of free wargames rules for playing a fantasy version of Roman chariot racing. What I like about these rules is that they don’t require you to play on a gridded board, like Circus Maximus and other chariot rules sets.
Pictors Building Guide
Pictors Studio has some great ideas for making wargames buildings out of foamcore. They also sell foam core blanks for buildings.
Siege of Tenochtitlan rules
Matt Fritz has these simple set of free wargamesrules for recreating the Siege of Tenochtitlan. He uses them with his students — a great idea for both wargaming and learning! It inspires me to try similar things in my classroom.
DBA Terrain Squares
David Kuijt has instructions on building terrain squares for DBA miniatures games.
1889 Colonial Uniform Guides
This is an excellent resource for colonial wargamers. Warflag has a number of nice color plates of French, German and Italian colonial uniforms from 1889.