Planet 28 is a set of free wargames rules for “quick narrative games between warbands of warriors, mutants, and outcasts.”
science fiction
Warpath Rules
Mantic offers its Warpath science fiction rules free for the downloading.
Deadzone Rules
Mantic offers a free pdf version of its Deadzone science fiction rules. I played these at a convention in recent months and enjoyed them very much.
Laserblade Science Fiction Skirmish Rules
Laserblade is a set of free wargames rules for science fiction skirmishes.
Building A 3D Space Hulk
Although it was essentially a rip-off of Aliens, as a game, Space Hulk was one of GW’s best game efforts. Here’s a tutorial on building your own 3-D Modular Hulks.