ToyMallet 40 cents is both a set of fairly well-done generic science fiction rules and a brilliant parody of the Warhammer 40K franchise. Written by Jennifer Reitz, it allows you to use any toys you happen to have, instead of spending many hundreds on “official figures.” The photos of the Hello Kittau Neko-Wai Meowarriors are a scream.
science fiction
Modeling Alien Plants
Terragenesis has a nice article with ideas for modeling alien plants.
Bugs Miniatures Rules
Brian Gill offers Bugs!, a set of miniatures rules for staging battles with large numbers of plastic insects.
Star Wars Miniatures Mass Battles Conversions
Arthur Chang has written a set of add-on rules for playing massed battles with the Wizards of the Coast rules for Star Wars miniatures.
Star Breach Sci Fi Rules
Star Breach is a set of science fiction rules that are miniatures agnostic. The free 1st edition core rules are available at the link. There’s also a deluxe version you can buy.