World Wind is an application being developed by NASA Research and Development for the NASA Learning Technologies program. From their website[1]:
“World Wind allows any user to zoom from satellite altitude into any place on Earth, leveraging high resolution LandSat imagery and Shuttle Radar Topography Mission (SRTM) elevation data to experience Earth terrain (or any planet with the data) in visually rich 3D, just as if they were really there. Virtually visit anyplace in the world. Look across the Andes, into the Grand Canyon, over the Alps or along the African Sahara.”