Earth Expects is a set of free wargames rules for space combat. The authors write:
Earth Expects is a highly detailed set of tactical space combat rules which emphasise skill over firepower. It is well suited to playing battles from duels to squadron actions; because of the high level of detail large fleet battles can be slow to play and therefore optional rules are provided to speed play in these games.
Titan Rampant is a free variant for the commercial Dragon Rampant rules. Ownership or access to Dragon Rampant is required for play.
Warlord Games offers a set of free quick start rules for their science fiction small unit game, Beyond the Gates of Antares.
Cybercity Blues is a free RPG that has a lighter take on the cyberpunk genre. The authors write:
“Cyberblues is a bit like Cyberpunk, only more mellow.”
Cyberblues City is a near-future, action-adventure roleplaying game. Fast-playing and often funny, it offers a lighter take on the cyberpunk genre, both in terms of system and tone. Cyberblues City uses a much modified version of the Fudge roleplaying system designed to make it easy on GMs. And best of all, it is absolutely free.
Black Skies is a set of free wargames rules for star fighter combat. The author writes:
A while back I was looking for something new to play and decided I’d like to try a star fighter combat game. I checked out a variety of rule sets and found nothing that I really liked. In fact, the most popular set seemed to be unnecessarily complex and slow, not something I expected from a set of star fighter rules. What I expected fighter combat to be was FAST. Complex and slow just didn’t work. So I set out to create my own (with plenty of help from the guys at my local war gaming club). I tried and liked an unfinished set by Shaun Austin which had several good ideas, but I thought the turn sequence could be streamlined. Using the basic card movement idea, and a simple combat system I tried to make these rules feel more like the fast deadly action I imagine star fighter combat should be.