EGBZine is an online archive of more than 10,000 pages of Edgar Rice Burroughs goodness — stories, articles, art and more. If you’re contemplating (as I am) a John Carter of Mars game, this is a good place to start.
science fiction
Classic Battletech Rules
Classic Battletech is a free 24 page set of rules for playing the original game of giant robots on hex maps.
Full Thrust Cross Dimensions
Full Thrust Cross Dimensions is a Full Thrust rules variant. It brings together rules from the various books and tries out some new ideas.
Hostile Stars Science Fiction Fleet Actions
Hostile Stars is a set of free wargames rules for fighting fleet actions in the Dark Realms universe.
All Quiet On The Martian Front Rules
All Quiet On The Martian Front is a great game set in an alternate history where HG Wells’ Martians return in 1908. It’s got a WWI vibe, with steam tanks and big cannons and motorcycles. You can take a look at the free rules here.