TurboSquid - TurboSquid offers 3D models for professionals.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
STLFinder - The 3d models search engine.
ZBrush - ZBrush is a digital sculpting and painting software solution.
3DOcean - 3D Models & Accessories From $1 for 3D Models, Textures, Materials & Shaders, 2D Concepts...
Cinema 4D - Cinema 4D is a 3D modeling, animation, motion graphics and rendering application.