3D IMAGING, MODELING and SPECIAL EFFECTS
SketchUp - Google's 3D modeling program for standalone modeling and integration with Google Earth (Mac and PC)
Maya - Sophisticated 3D modeling program. Steep learning curve, but if you need lots of 3D, its worth knowing about. (Mac and PC)
Motion - Part of Apple's Final Cut Studio package. Very powerful, intuitive 3D and special effects program (Mac)
After Effects - Adobe's Long time standard special effects and 3D program. (Mac and PC)
Fledermaus - Excellent 3D modeling program. Especially useful for modelling real world data that is geospatial in nature.

3D VIRTUAL GLOBES - digital renderings of the world drapped with high resolution satellite imagery and other layers.
Google Earth - PC, Mac and Linux. The one and only. Available in six language versions
ESRI's ArcGIS Explorer - Designed to primarily interact with data from ArcGIS and ArcGIS Server, but offers full featured 3D support. PC only
Microsoft's Virtual Earth - PC only
NASA's WorldWind - PC only, Mac compatibility coming