Google Earth requires a free download.
The following are some ideas for using this tool across the curriculum:
Math: Real World Math offers a nice collection of math lessons using Google Earth. Some ideas include measuring distances, angles and elevations of real world locations.
Science: Google Earth has many built-in layers applicable to teaching science. The sky, moon or mars modes offer students the ability to visit these places and explore! It also includes access to earthquake data, climate data and animal tracking information.
History: Use the timeline view to compare views of cities from past to present. Students can create tours of military campaigns or explorations or go on virtual field trips around the world.
Art: Use Google Earth to explore inside actual art museums around the world! This is currently available for 17 galleries, including places such as the Freer Gallery of Art in Washington D.C., the Metropolitan Museum of Art in New York City, and the National Gallery in London.