Free Stuff
Internet Archive
Books, games, movies, music, software, televison.link
The internet archive has a wide range of content offerings for completely free. I personally use it for CD rips and old concert recordings, though they've got games, movies, and books freely available as well. Some stuff you can download, but a good chunk is only viewable on the site. There are ways of getting around this though.
Bandcamp
Musiclink
I haven't explored it all that much but some bands and artists post free albums on here. One notable band is King Gizzard and the Lizard Wizard, which has made all of their albums name your price after removing their discography from Spotify. They also have concert recording available on their "bootleg gizzard" page.
MangaDex
Mangalink
MangaDex is a pretty high-quality manga reading site, compiling many translations in lots of languages into a simple interface. It has had some copyright issues recently, so the selection now certainly isn't as good as it was.
Vimm's Lair
Game ROMslink
Vimm's Lair is a pretty useful rom site that's been around for a while. This is usually where I go to get roms first, since the speeds aren't bad at all, unlike sites like the Internet Archive. However, this is another site that has had copyright issues, so it's missing a good chunk of games for certain systems.