Sketchucation - Sketchucation is a 3D SketchUp Community for students, professionals, designers, and hobbyists.
CGTrader - CGTrader is an online marketplace at which artists can sell and buy Revit and 3D models.
CGTips - CGTips is a 3D Architectural Visualization learning platform for Architects or interior designers to build their skills in an interactive way.
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
TheSketchupEssentials - TheSketchupEssentials is a community to get SkethuUp tutorials and help from professionals.
TurboSquid - TurboSquid offers 3D models for professionals.