Stars Without Number
Resources
The completely free rulebook.
A list of free official supplements.
If you've tried the free rules and know that you'll keep playing them, I can totally recommend the Core Edition - it adds two big chapters about AI/mechs and generating planetary societies.
Another supplement I've also gotten a lot of use out of is Suns of Gold. The tables and rules for interplanetary trading has been really useful to flesh out my worlds even more.
A really cool random sector generator.
A campaign in the SWN universe, as played live on Twitch. The DM is the co-creator of the also pretty cool Dungeon World, which you can also watch being played here. Can you tell I kind of like that channel? ;)
A Mass Effect campaign setting. I haven't tried this yet, but it looks cool.
Tables of buyable (and some unbuyable) items.
Sektoren (ab hier auf Deutsch)
Hades Theta