Thanks to a notice by TechRepublic, here are five utilities for use with Google Earth:

• SketchUp (of course!) to create 3D models for Google Earth.
• RoboGEO is a utility for geo tagging image files.
• Google Earth KMZ or KML to GPS Converter to convert Google Earth data to a GPS compatible format (a .GPS file).
• The Google Earth API to display Google Earth (and any custom features) within a Web browser.
• Cache for Google Earth to be used while working offline.