GrabCAD - Helping mechanical engineers build great products faster
CGTrader - CGTrader is an online marketplace at which artists can sell and buy Revit and 3D models.
Vecteezy - An online marketplace where users can license stock photos, vector graphics, and stock footage directly from artists. Basic features are free but include ads and limitations. Pro subscribers get advanced licensing and a wider selection of content.
3DExport - 3DExport is a 3D model marketplace where you can buy and sell 3D models, CG textures and digital objects for 3D printing with royalty free. Professional 3D models - 3DExport.com
motosha - Real free high quality stock photos for commercial and private use! From selected professional photographers. Simple download without registration, without obligations. Best quality and 100% Free.
TurboSquid - TurboSquid offers 3D models for professionals.