Archive.org - Various
Zomb's Lair - Videogames
The Collection Chamber - Videogames
Legends World - Videogames
r/roms Megathread - Videogames
Emulation Wiki - How to get those games running
The Asenheim Project - Visual Novels
Mangadex - Manga (always make sure you're on the real mangadex)
Dynasty Reader - Yuri Manga mostly (kinda horrible place, though. just read then run)
Lovely Strange Dark - Manga
Lililicious - Yuri Manga
Old Castle Fansubs - Old Anime
Libgen - Books (wikipage for hopefully up to date links)
Anna's Archive - Books (ditto)
Arkm's World Lib Online List - Books
Open Library - Books

indexes

https://wotaku.wiki/
https://fmhy.net/
https://r-roms.github.io/