Sketchucation - Sketchucation is a 3D SketchUp Community for students, professionals, designers, and hobbyists.
CGTips - CGTips is a 3D Architectural Visualization learning platform for Architects or interior designers to build their skills in an interactive way.
3dxo.com - 3dxo.com is a great place for both professionals and hobbyists to find some really cool, free 3D models.
TheSketchupEssentials - TheSketchupEssentials is a community to get SkethuUp tutorials and help from professionals.
3Dmdb - 3Dmdb is a search engine-based hub of multiple three-dimensional colorful objects which can be downloaded, purchased, and rendered from shops or marketplaces.
Texture Haven - High-quality PBR textures for free to everyone, with no catch.