Chris Brantley has collected this list of rules variants for the De Bellis Antiquitatis (DBA) ancients miniature wargame.
rules
1 Page Napoleonic Skirmish
The Jackson Gamers have these free wargames rules for Napoleonic skirmishes. The best part: the rules are just one page long.
Ares Fantasy Skirmish Demo rules
Majestic 12 games offers these demo rules for their Ares fantasy skirmish miniature wargames system. They explain:
ARES: Miniatures Wargaming System is a complete skirmish-level fantasy game. But it is also much more. The flexibility of the system allows players to use any wargaming miniatures in their collection. Over two dozen sample figures are detailed in this book, but the real strength of ARES is its figure creation system, that encourages players to use their imaginations — which is the way it should be! Also included is a fully-customizable magic system, providing players with the opportunity to design their own spells for their troops.
Starmada demo rules
The Starmada demo miniature wargaming rules are available from Majestic 12 games:
Starmada is a simple (but not simplistic) board game of starship combat, in which players square off in a general attempt to blast each other’s fleets into just so much space junk. While the universe of the Imperial Starmada and its major adversaries is fully detailed in the rulebook, Starmada is much more than just another game, tied down to its own background. Instead, Starmada can be played in just about any science fiction setting you can imagine. There are dozens of optional rules, exotic special equipment items, and menacing weapons that can be used or discarded at your discretion, to create the type of game you want to play!
Hougoumont Battle Rules and Scenario
From Matt Fritz comes this set of rules for using wargame miniatures to replay the fight for Hougoumont from the Battle of Waterloo.