When I first learned about making placemarkers in GoogleEarth and saving to a KMZ file, I was really excited but I knew there would be a problem for schools where bandwidth was an issue. I had a recent session with Alice Christie where she showed her site about Google Treks, which uses Google Maps, and therefore less bandwidth than Google Earth. Take a look at her site, make your own Google Trek, and submit it to her site!
It's pretty simple to make a placemarker in Google Maps (or Google Earth, if your district has the bandwidth) and create a virtual field trip!
Be sure to go to Google Lit Trips to learn about making these virtual field trips!