The Singapore miniature wargaming group that calls itself the NapNuts offers a page of Napoleonic Uniform Guides.
The Evolution of Napoleonic Uniforms website is an ambitious work. It is not by any means complete (could any project of this scope ever be complete, given the number of variations?), but is worth browsing through.
Inferno Games offers a set of free wargames rules called "Factions". It's designed for 25mm to 28mm skirmish games. Here's what the authors say:
Factions is a squad based game of warfare between rival gangs. Many stories could be created as to why they are at war with each other. The Core Rule book covers all the rules you will need to begin playing. It includes:
* Short guide on how to play.
* Rules for creating a Space Marine Faction
* Weapons & Equipment
Factions is similer in many way to a plethora of Games Workshop games (because that is what we based it on). It resembles, in my opinion, a mix of Inquisitor, Necromunda and Mordheim. To play you also recquire many dice including d4, d6, d8, d10, d12 and d20. Also having a d% (a dice with 1-10 on in and a dice with 10, 20 30 ect.) is helpful, although it can be made by having two seperate coloured dice.
North Against South is a set of free wargames rules for civil war battles. It's based on the boardgame Battle Cry by Richard Borg.
Fight Dice is a set of free wargames rules that uses a neat dice pool system, where the players allocate handsfull of six sided dice to their actions.