This page exists as an place to gather and describe sites that offer 3d models.

https://www.thingiverse.com/

http://www.bld3r.com

http://www.yeggi.com

(still hosts thingiverse files)

http://www.repables.com

https://www.youmagine.com/

"YouMagine is an online community of 3D printing enthusiasts who wish to work together to share, remix and make better 3D printed things. YouMagine facilitates this community, empowers and gives you the tools you need in order to improve, invent & make."

https://cubehero.com/

https://pinshape.com/

https://www.stlfinder.com/

https://www.makesea.com/

https://www.myminifactory.com/

https://grabcad.com/

https://cults3d.com/

Some of the content here was derived from: https://www.reddit.com/r/3Dprinting/comments/26do2z/alternative_repositories_to_thingiverse/