The 6mm science fiction Yahoo group is very active and has a number of nice rules sets. Maximum Firepower is one designed to be played on a hex grid, and it uses something called the BattleStory system, which it describes as a “universal mechanic that, with the roll of color coded dice, tells you: 1. What orders were issued? 2. How did the troops perform? 3. Who won the battle, and why? 4. What happened to the survivors?
The New York Public Library has a large collection of color plates of the armies of Finland in the 18th and early 19th centuries.
Here are a set of houserules called Fields of Honor. I can’t tell whether they’re houserules FOR the Fields of Honor set, or a set of houserules BASED on Fields of Honor. I lean toward the latter. They look like a fairly complete set that bears more than a passing resemblance to the original Fields of Honor set published a decade or so ago by Pinnacle.
Eric Wood offers a set of free wargames rules for playing the 100 Years War battle of Crecy
Here’s a large selection of color plates of the uniforms of Norway and Sweden from 1500 – 1909.