I am a computer lab teacher, but taught 2nd grade for 3 years. In the classroom, we used Google Earth in science to view the locations where different dinosaurs were found. We also used it to visit the homes of different animals and learned how their habitats were different. Lastly, we had ePals in various countries. We used Google Earth to "visit" the homelands of our ePal friends.
I am the librarian at my elementary school. I use it to compare the printed atlas and the global placement of countries. It really brings mapping (a SS skill) to life. Our little ones also have had problems confusing a city and a state. GoogleEarth seems to help a couple of them make the distinction that the city is inside the state. My 2nd graders participate in a Christmas/Holiday card exchange through iEARN.org and we use GE to locate the country that sent us the holiday cards. My 5th grade studies WWII and we use it to locate countries and visit cities.