Warp Portals should be useful for a variety of science-fantasy games. Here’s a simple but effective technique.
science fiction
Hitchhiker’s Quest For The Galaxy Game
Hitchhiker’s Quest For The Galaxy is a home-brew card game based on the book of the same name.
You gotta love a game which specifies that “the most depressed player goes first.”
Free Warhammer 40K Building Paper Model
For Warhammer 40K fans, here’s a paper model of a multi story building designed for the game.
Mutant Future RPG
Mutant Future is a retro-clone of the old TSR Gamma World Game. There’s a commercially available printed version, but you can also download an artless version if you just want the rules.
Mutants and Machine Guns RPG
Mutants and Machine Guns is a free RPG set in a post apocalyptic future. It is simple enough that it fits into the terrific PocketMod format.