Hulks and Horrors was an unsuccessful Kickstarter effort, but now is available as a free pdf.
Miniatures Rules
Operational Art WWII Rules
Operational Art is a set of operational level WWII rules.
Border War Fantasy Skirmish Rules
Border War is a set of fantasy skirmish rules.
The Chaco War 1932 – 1935 Wargames Rules
The Chaco War is a set of free wargames rules based on Phil Barker’s DBA. It’s designed to let players fight out the 1932 – 1935 Chaco War, which was fought over control of great part of the Gran Chaco region of South America, which was incorrectly thought to be rich in oil.
Mimi and Toutou Go Forth WWI Naval Rules
Mimi and Toutou Go Forth is a set of simple naval rules for WWI naval battles on Lake Tanganyika. Obscure, to be sure, but intriguing.