Looking for an alternative to Warhammer 40K? Who isn’t? This may be it. Even better: these wargames rules are free. Ivan Sorensen’s Fast and Dirty rules also would work for modern combat.
science fiction
Modeling A Void Shield Generator
Here’s a tutorial on scratch build a void shield generator. While intended for Warhammer 40K, a model like this could be used in a lot of science fiction games.
Spaceship Miniatures and Games List
Tom’s Spaceship Miniatures / Games List offers a nice resource for people getting into this type of gaming. FWIW, Silent Death is one of my all time favorite games.
Kryomek Science Fiction Rules
Scotia Grendel now offer their classic Kryomek science fiction skirmish rules as a free download.
Installation 42 Print-And-Play
Installation 42 is a free print-and-play deck building game with a science fiction theme. Looks good.