The Iron Hand site has a tutorial on building a very nice building-sized laser defense battery for 25mm – 28mm science fiction games, such as Warhammer 40K. These would be great as the focal point of a scenario.
Science Fiction
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.
Space Rat RPG
Space Rat is an RPG written by Nathan Russell in just 24 hours. It’s inspired by the cheesy science fiction movies of the 70s. It looks like a lot of fun.
WarZone Photo Gallery and House Rules
Redjack has an attractive photo gallery of figures from the late, but great Warzone game. I’ve got a ton of those figures myself.
There also are a couple of Warzone scenarios and house rules
Legends of Time and Space RPG
Legends of Time and Space is Dark City Games’ rules set for tactical science fiction role playing. It’s based on the well-loved, out-of-print Fantasy Trip system.