We have used GE in conjunction with the fourth grade landforms unit. Students needed to research three different landforms in the US and find an example on GE. They created a placemark that included information about the particular landform. I set up a scavenger hunt for Grade 2 where they visited different continents, measured distances between places, etc. We also used the polygon tool to outline different regions of the US. I'm also looking for more lessons at the elementary level.
In Grade 1, I just teach them how to use the basic controls and fly around. Grade 2 and 3 study geographic landforms at our school so that fits well. The Grade 4s study latitude and longitude so we do a little scavenger hunt there.
The Grade 5s plotted out the life of a certain explorer using placemarks. At each point, they had to provide information on the significance of that placemark.
The overlays that you can download on the Internet are great as well. There is an overlay of deforestation in Brazil that is really shocking.
I used Google Earth for the first time this year in my classroom with one of my team mates for social studies. We used it as we talked about the different continents and oceans. We allowed the students the opportunity to explore each continent as a team up close. Later in the year we used it to help students make a community map. Students explored several place around the world. Google Earth allowed them to look at an area from several perspectives. Use cardinal directions they traveled down streets to see various things in the community.
I have used GE to "fly" the students to the locals of the different eras, i.e. when we started our Mesopotamia unit we took the students on a virtual field trip to the Tigris and Euphrates, when we were in the Egyptian unit we "flew" to the Pyramids. The 3-D effects and the flying from our school to the location gave the students a better idea of the places we were discussing.
I use Google Earth from kindergarten on. It's a favorite with both students and their parents. I've attached an introductory lesson that collaborates with the first grade inquiry into national symbols. I Introduce Google Earth, how to pan in and out and change perspective with the mouse, how to see the sunrise line (they love this), use Sky, and use Street View to see their house (if they're lucky. If not, they see their neighbor's).
Under Google Earth community, you can find a tour of CA missions (for third grade) or create one with the placemarks and picture overlays. I'm looking forward to using the Mars and Undersea elements they have added this next school year.