The Water Margin is a set of free wargames rules for oriental skirmishes.
The Miniature Wargaming Editor
Mixing Citadel Paints
Path of the Outcast has a nice illustrated tutorial on mixing a base set of GW paints to come up with OTHER GW paints. For example: Chaos Black + Sunburst Yellow + Enchanted Blue = Scaly Green
WWII Plastic Skirmish
Brett Drake offers a set of rules called WWII Plastic Skirmish, which are — obviously — rules for playing WWII games with plastic army men.
What more could you want? Your favorite childhood toys. Dice. Mayhem.
Napoleonic Wargames Rules
Steve Burt offers a set of Napoleonic Wargames rules.
Burrows and Badgers Rules
Burrows and Badgers is a set of free wargames rules for tabletop adventures with bands of anthropomorphic animals. There’s also a supporting set of miniatures.