Images, Illustrations, vectors, videos:

https://pixabay.com/
https://unsplash.com/

 

Stock footages:

http://mitchmartinez.com/

 

Sound, music:

https://freesound.org/

 

Hdri:

http://www.hdrlabs.com/sibl/archive.html

 

Fonts:

https://www.dafont.com/

 

3d Models:

https://www.blendswap.com
(20 downloads a month)

 

32 full textures pack:

https://www.poliigon.com/search/recent/narrow/list/free%20textures

 

Textures:

https://www.textures.com/
(formerly cgtextures.com) – 15 credits a moth.