WWII: All the places, battles & special OP
And the great links make it even more valuable.

Anchorages of the Caribbean & More
Anchorage placemarks utilize anchor icons, placemarks which include diving information have dive flag icons, and land based travel utilize either sign posts, Myan pyramids or airplanes. Icons are grouped by region / country / state or year.

California Historic and Geologic Maps
Still fine tuning the interface and adding more maps. Now have about 1,700 map overlays available. I have also color and size coded the image placemarks so that it's much easier to tell where the maps are in relation to each other. Any of the map groups that have "NEW" at the end have been converted over to this index system. Working on converting the others over.

Sculptures Around the World
am new..and as the warning notice suggests, am bubbling with enthusiasm.How about collecting sculptures that actually can be seen on Google Earth. OK, if you want to add museums as well that may be OK and note the presence of a sculpture garden or what have you.
I was just amazed at that I could see Henry Moore's Atom Piece (Nuclear Energy) on the U fo Chicago campus.

Airports Worldwide – over 950 of them!
What started out as a little pet project to find the airports that I had flown to, ended up being a massive undertaking of international proportions