The Great War Naval Rules is a very comprehensive set of rules for WWI Naval warfare.
rules
Combat Captain WWII Rules
Combat Captain is a set of free wargames rules in which the basic unit is a company consisting of up to eight squads. Author David Raybin says that the rules “allow a high degree of flexibility in unit activity during a turn. The idea is simplicity of play so the game will move along to a satisfactory conclusion in under three hours.”
Kraken: Victorian Man Against Sea Monster
Matthew Hartley has a game called Kraken, inspired by the man against sea monster scene in Jules Verne’s 20,000 Leagues Beneath the Sea
Expanding Space Hulk
Game Workshop’s Space Hulk game is one of the best it’s every produced. Every game is fraught with tension, as the marines attempt to maximize their scarce action points in the face of an increasing onslaught of genestealers. With good players, this game is nearly always a near run thing. Unfortunately, like so many of their efforts, the Evil Empire hasn’t continued to support it. Expanding The Hulk is a website dedicated to continuing the Space Hulk game. It’s got rules for using many of the other races in the Games Workshop universe, including Chaos, Eldar, Dark Eldar, Necrons, and Orcs.
Event Horizon Starship Combat Rules
Event Horizon is a set of free wargames rules for quick play starship combat. It is played on a grid board.