A Hotter Fire is a set of free wargames rules for naval combat between civil war ironclads.
Rules: American Civil War
American Civil War Campaign Rules
The DFW Grognards have published a set of ACW Campaign rules.
Give Them Cold Steel Civil War Rules
Give Them Cold Steel is a set of free wargames rules for the American Civil War.
Ironclad American Civil War Naval Rules
From the Naval Wargames Association comes Ironclad, a set of free wargames rules for ACW ironclads.
Howlin’ Mobs ACW Rules
Howlin Mobs are a simple set (five pages) of ACW rules for big battles.