Ed Walker has written a set of free wargames rules called Tabletop Titans. He writes:
BAM – POW – KAZOWEE. These are the sounds of super heros in action. Who could forget the wild brawls we all envisioned while reading our favorite super hero comics? Tabletop Titans is a game of miniature combat where players create super heros to do battle. Designed to be played on any tabletop or with one of the many types of terrain systems on the market Tabletop Heros provides all the rules necessary to create a unique super hero and pit it in combat against other superpowered beings. Tabletop Titans uses the ACTION combat system.
Age of Blood is one of the best set of rules available for free on the internet. Heck, its one of the best available at any price. Designed by Tom Hinshelwood, the second edition rules offer a complete game and campaign system for the age of Vikings.
Age of Blood is a skirmish-level battle game in which players take control of bands of Vikings and lead them on bloody adventures in search of loot and glory. These rules contain all the information you will need to know in order to play either one off games or complete campaigns. The game is designed for use with 25mm or 28mm miniatures, though any individual based model from 15mm to 40mm can be used. Play is possible with any scale but distances and measurements would need to be proportionately reworked. Age of Blood�s focus is on the fantastical aspects of Viking history and as such is more concerned with the legends and heroic sagas then trying to depict a realist view of the era. These rules are loosely set in the 9th Century, though the supernatural is prevalent in many aspects of the game including fate, magic and monsters. If desired though the supernatural elements to the rules can easily be ignored so that the game can be played as a purely historical wargame.
Other Age of Blood Resources:
Interformic Games offers a free miniatures game called Turn or Burn. The authors write:
Turn or Burn is a fast-paced game of space fighter combat for 2 to 8 players. To start a game, you design your fighter from a deck of system cards. Each turn you play a system or maneuver card facedown to plot the action your fighter will take. The game uses vector movement, so you must plan ahead! When everyone has plotted, all players reveal their actions simultaneously. Fighters move, guns fire, stuff explodes, and it’s on to the next turn.
There also are several modules for more detail.
There are some nice color plates on this site showing the uniforms of the German states in the 1700s. I don’t know German, but by looking at the plates, I think that they’re all from the Seven Years War. The first page is definitely Frederick the Great and his generals. Someone with more epertise in either the period or in German will have to provide more detail.