Some years ago, Wargames Foundry published a set of rules to go with their Street Violence figures. They’re missing — as far as I can tell — from the Foundry site, but you still can get them as a free download at The Warstore.
Rules: Science Fiction
Legends of Dying Mars John Carter Skirmish Rules Set
Legends of Dying Mars is a set of free skirmish rules for playing games set in the classic Edgar Rice Burroughs John Carter of Mars Barsoom setting.
The AD Wars Science Fiction Rules
The AD Wars is a set of free wargames rules that are adaptation of Warhammer Ancient Battles for science fiction games. It’s interesting. You will need a copy of Warhammer Ancients to play, though. But there are a lot of copies of that out there.
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FUBAR One Page Modern / Science Fiction Rules
Fubar is a good looking one page set of modern and science fiction rules.
Free 3D Terrain For Dust Tactics
Top Solitario, one of my favorite sites for its quality free paper products, has a selection of 3-D terrain pieces for Dust and other games which can be downloaded, printed and quickly constructed — a bonus is that they also fold flat!