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.

Grand Fleets demo rules

Majestic 12 games has these demo rules for their Grand Fleets miniature wargame. My group has played these and really enjoys them. Majestic 12 explains:

Grand Fleets is a comprehensive miniatures game of dreadnought-era naval warfare. In addition to rules for everything from ships to aeroplanes, Zeppelins to submarines, the rulebook includes:
Data cards for over 120 ships, plus guidelines for converting any ship of the period to game values; Eight scenarios encompassing conflicts from the Sino-Japanese War of 1894 through the opening salvoes of World War Two, including several variants; Fifteen pages of weapon data, covering all major gun and torpedo models in use through 1939, over 200 aeroplanes, and more than 20 airships; and Optional rules for flotillas, night-fighting, smokescreens, and more!

ECW Rules

The Jackson Gamers have this set of free wargamesrules for the English Civil War. They use a card activation system, (not surprising, considering the acknowledged Brom influence), and d6s to resolve actions. These rules are 20 years old and in their 6th edition, so they are well-tested.

For The Masses demo rules

Majestic 12 Games has these demo rules for their For the Masses Fantasy miniature wargames system. Here’s their blurb:

For The Masses is a complete fantasy mass-combat wargame system. But it is also much more: The flexibility of the system allows players to use any fantasy setting and armies to play out famous fantastical scenarios and ancient epic battles. Several sample army lists are included in the book but the real strength of For the Masses is the unit creation system. This system encourages players to be creative, use their imagination and have fun, which is the way wargaming should be.