The Free Software Catalog
Just about anything you want to know has been - or is being - cataloged into a database or encyclopedia - i.e. wiki - of some kind.
Here is a great list of free, high-quality reference material available to anyone with a web connection.
Released: Oct 26, 2011
Google Earth lets you fly anywhere on Earth to view satellite imagery, maps, terrain, 3D buildings and even explore galaxies in the Sky. You can explore rich geographical content, save your toured places and share with others.