I got tired of fandom wikis, so I've built a fictional planet directory
Every time I wanted to remember what a planet from a novel actually *was*, I got one of two things: a fandom wiki with forty paragraphs of in-universe trivia and no sense of why the place mattered, or nothing at all. Lem, Le Guin and Simmons especially — their worlds are the whole argument of the book and they're barely written up anywhere.
So I started writing them myself. One paragraph per planet: what it is, and what it does to the story. It turned into a site — link in the comments since I'm not sure about the self-promo rules here.
141 planets, 22 universes so far. Star Wars and Star Trek are the biggest sections because they're the easiest, but the ones I actually enjoyed writing were Gethen, Anarres, Hyperion, Regis III from The Invincible, and Rakhat from The Sparrow.
https://www.fictionalplanets.com/ — a small reference site for planets from science fiction.