Here are some links to useful information and resources.

• Bentley
• Geopak Civil
• In-Roads
• Autodesk

• Archvision Real People Content : 3D content, image based trees, people and cars
• Onyx Tree : Source for 3D Tree and Plant Parametric Modeler
• Digimation : Source for 3D models and textures
• Image Cels : Source for 3D models and textures
• Marlin Studios : Source for 3D Models and Textures
• ModelVision : Source for 3D models and textures
• Turbosquid : Source for 3D models and textures
• Okino Graphics : Conversion an publishing software for 3D and image based formats
• Right Hemisphere : Conversion an publishing software for 3D and image based formats
  

• Adobe
• Discreet
• Eon Reality : Realtime 3D authoring tool
• Anark Studio : Realtime 3D authoring tool
• Quicktime
• Cortona VRML Viewer
• Keyhole : Satellite Image Streaming Viewer

• 3D Industry Forum : An organization whose goal is the further adoption of 3D interactive technologies through the promotion of 3DIF technologies and standards, including Microsoft's U3D (Universal 3D)
• TRB Viz: Transportation Research Board's Task Force on Visualization Web Site
• Urban Simulation
• National Center for Simulation
• Digital Earth : Collaborative Geotech Weblog