Free iPad app: https://itunes.apple.com/us/app/google-earth/id293622097?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/google-earth/id293622097?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.google.earth
Free Mac program: http://www.google.com/earth/download/
Free Windows program: http://www.google.com/earth/download/
Google Chrome app: http://www.google.com/earth/explore/products/plugin.html
Mozilla Firefox extension: http://www.google.com/earth/explore/products/plugin.html
Apple Safari extension: http://www.google.com/earth/explore/products/plugin.html