For those of you who want to learn to program your own Google Earth plugin applications, the place to start is the Google Earth API web site. Here you will find links to the Google Earth API Developer Guide, the Google Earth API FAQ, the Google Earth Browser Plugin forum, and a link to the Google Geo Developer Blog.
All of this will become even more important in the not too distant future. Google will be releasing new improved versions of the Google Earth API and plugin including support for Mac OS X for the plugin. Hopefully the new API will include support for more built-in Google Earth layers, and more straightforward functions to turn on and off KML content.
About Frank Taylor
Frank Taylor started the Google Earth Blog in July, 2005 shortly after Google Earth was first released. He has worked with 3D computer graphics and VR for many years and was very impressed with this exciting product. Frank completed a 5.5 year circumnavigation of the earth by sailboat in June 2015 which you can read about at Tahina Expedition, and is a licensed pilot, backpacker, diver, and photographer.