Iron Brigade is Mike Willegal's third edition of his Civil War rules. It's designed on a 1/20 scale.
Republished by Blog Post Promoter
ACW Sh*t For Real Men is a set of free wargames rules for grand tactical battles in the American Civil War. It's designed for 15mm figures.
American Civil War Riverine Actions is a set of free wargames rules for ironclads, tin-clads, cotton-clads and all the fun and unique ships that plied the rivers of the United States during the ACW.
The Battle of Blackburn's Ford is an introduction to the Combat Command American Civil War Rules. The pdf also includes counters if you don't have figures.