I am going to start working on a Google Earth loader for Xith soon. The Google Earth format (.kmz) is basically a zip file containing a COLLADA file plus texture images. The free modelling tool Google SketchUp supports export to this format.
http://download.sketchup.com/OnlineDoc/gsu_win/K-Input_and_Output/Import_and_Export/IO-KMZ-Export.htm
http://sketchup.google.com/
This will give us access to the models in the Google 3D Warehouse:
http://sketchup.google.com/3dwarehouse/
See also:
http://earth.google.com/
