Iron Cow is a set of simple rules pitting companies and battalions of science fiction and armor against each other.
Blasted Planets is Lance Runolfsson’s set of free science fiction skirmish rules to support his line of miniatures. Lance writes:
Blasted Planets Skirmish, is basically a set of house rules a few friends and I use to play games with my Sci-Fi figures. I am not trying to model a “Hard” Sci-Fi environment here. I’m borrowing as much from Horror and Fantasy as I am from Sci-Fi. I mean how serious can you be. When you have, Dog headed, Gator men chasing an Elephant guy around an Omni Field generating White rabbit? There is enough “real” world framework here that basic tactics work (most of the time). But enough of a fantastical element that you really can’t count on the idea that the Fin headed alien with the pin gun is going to nail the cave man with the rock every time.
Roar of the Crowd is a set of free rules for playing science fiction, fantasy or historical gladiator games.
Here’s a link to a set of Dr. Who miniatures rules.
Astral Dreams is a free miniatures game based on the d20 Open Gaming License system. The game’s background is based on a short story of the same name, which involves a war between humans and robots.