This list is now a part of my other list
A list of websites where you can download stuff for free. Please feel free to contribute.
Inspired by this
Audio books & ebooks
Audio/music
Indie Games
Stock Images
Software
Icons
Data
US Bureau of Economic Analysis
Project Euclid -- Mathematics papers
Organization for Economic Cooperation and Development
Development
Loading.io -- Make loading icons
Placeholder -- Placeholder images
Open Game Art -- Game assets
Other
Thingiverse -- 3D printer models
Archive.org -- Music, movies, books, software, etc
Cube Craft -- Paper models
Hubble Space Telescope -- Top 100 images
Galbadia Hotel -- Video game soundtracks
Myabandonware -- Abandoned Games
the-eye -- Archive project (old books, games, websites, music, etc)