Sketchucation - Sketchucation is a 3D SketchUp Community for students, professionals, designers, and hobbyists.
Img.vision - Image hosting & video hosting for eCommerce sellers
CGTips - CGTips is a 3D Architectural Visualization learning platform for Architects or interior designers to build their skills in an interactive way.
UploadHouse - Thumbnail and resize your photos and images
3dxo.com - 3dxo.com is a great place for both professionals and hobbyists to find some really cool, free 3D models.
ImageVenue - ImageVenue is a great online hosting service that allows uploading pictures for showing creative works with a simple-to-use technique.