Free 3D Object Files
Collection of some of the sources available for free STL files.
Some services also provide higher quality files and/or printed objects for a fee. (Note: Since some of the 3d objects have a fee, think about what you're going to print and ensure that it won't destroy the printer)
3D Warehouse - collection of STL files and SketchUp files. The service is provided by Trimble.
3Dagogo - collection of files for free in addition to ones for sale. The service is provided by AstroPrint.
Autodesk - provider of one of the common 3D printing applications, they also have a collection of free 3D object files. The service is provided by Autodesk.
Cults - a leading source in the French 3D printing market with free STL files and higher quality files for a small payment.
GrabCad - main focus is on the mechanical engineers community with objects from jewelry to furniture. The service is provided by Stratasys.
MyMiniFactory - this source offers guaranteed STL files as each file is selected and tested by the community members. The service is provided by iMakr.
NASA - small collection of model files provided for free by NASA. Some files may need adjusting and modifications.
Pinshape - a large 3D printing community of over 55,000 manufacturers and designers. They have both free STL files and premium files for a cost.
Thingiverse - Started in 2008, Thingverse has a very large collection of STL files. The service is provided by Makerbot.
Threeding - contains files including ancient artifacts and synthetic animal parts. Both free and paid files.
Yeggi - very large collection of 3D models.
YouMagine - Collection of over 13,000 high quality open-source designs ready to print. The service is provided by Ultimaker.
MakerWorld - is an online platform offering a wide range of 3D models for download and 3D printing, catering to hobbyists and professionals alike. The service is offered by Makerworld, in connection with Bambu.
MakerLab - Online platform intended to be used in the creation of custom 3D models easily and effortlessly, whether for professional use or just starting into the world of 3D. The service is offered by Makerworld, in connection with Bambu.