Archives

http://textfiles.com
http://www.phrack.org

Images

https://images.nasa.gov/
https://www.rawpixel.com/category/53/public-domain
https://www.si.edu/openaccess
http://www.loc.gov/pictures/
https://www.flickr.com/photos/britishlibrary/albums https://www.moma.co.uk/public-domain-images/

Game Business

http://sloperama.com/advice.html
https://lostgarden.home.blog
http://www.gamesprecipice.com
http://www.designer-notes.com
https://www.psychologyofgames.com

Art for Games

https://www.gamedevmarket.net
https://assetstore.unity.com
http://www.supergameasset.com
https://graphicriver.net/game-assets
https://www.scirra.com/store
https://gameartpartners.com https://opengameart.org https://kenney.nl/assets
https://game-icons.net
https://www.reinerstilesets.de

Music

https://incompetech.com/music
https://www.hongkiat.com/blog/download-free-sound-effects