1906 San Francisco Earthquake Tour by USGS – This “geographic” kml contains information about the great earthquake, displaying fault lines and locations where damage occurred. The embedded photos bring the tour to life, especially those that put the 1906 view next to the current day.
Wild Sanctuary: The Voice of the Natural World – Wild Sanctuary is an organization devoted to capturing and cataloguing natural sounds found all across the world. Their kml file is very professional – clean informative and logical in its design. This file also includes sound – each placemark has an embedded sound player that gives you a brief example of the natural sounds of that location.
The Life and Times of Charlie Chaplin – A wonderful example of a tour used as a biography. This tour follows the life of Charlie Chaplin, from birth until death. There are photos of important locations and events along the way, and just enough detail to keep the casual viewer interested. A good place to start if you want to design an informative and entertaining tour.
On the Road with Jack Kerouac – An extremely detailed look at the life of the famous beat poet and philosopher. It’s one of the largest collections of placemarks I have seen in a Google Earth file. Good examples of changing the bird’s-eye perspective away from top-north and directly above, to make the flight from placemark to placemark more visually stimulating.
KML Samples – This file isn’t really a tour, but it contains a series of placemarks that you can use as examples of how to create and format your own placemarks. Very good resource for cutting and pasting html code.