The Wargaming Site Blog has a nice photo tutorial on making barbed wire emplacements for 6mm wargames figures.
Cuirassiers 1700-1870 is a set of free wargame rules for 18th and 19th century warfare. It is ideally for 6mm figures.
En Avant En Masse is Jim Wallman’s diceless, divisional level Napoleonic Wargame. Jim writes:
Based on the En Avant! diceless battalion level game, this takes the concept to the next level. This system is designed to play out a corps battle using 6mm figures in about an hour or so. The intention is that there is a player per division, with a corps commander in overall control, per side. It is not intended that the players see or use the game rules � this is to be done by one or more umpires.
Phalanx are a set of free wargames rules for ancients using 6mm figures. Figure scale is 1 to 4. Time scale is one minute per “bound.”
Solar Scourge is a set of free wargames rules designed for 6mm science fiction miniatures.