Elan Deluxe is a set of free rules for playing Napoleonic wargames. Once published professionally, it now is available online. This is a very well done, and interesting set of rules. The nominal scale is 1-50, with units representing battalions and regiments.
Hardtack is a set of regimental Civil War rules based on the excellent Stargrunt II rules. With a scale of 1 fire = 3-5 men, it’s intended for fighting one regiment v another, filling the space between Johnny Reb and Brother v Brother.
Iron Brigade is Mike Willegal’s third edition of his Civil War rules. It’s designed on a 1/20 scale.
Over the Hills and Far Away is a regimental campaign game from the fertile gaming mind of Jim Wallman.