xplanet is a GPLed program, written by Hari Nair, that is similar to the older program xearth. It is also compatible with it (supports the same marker file format).
xplanet displays Earth (or any other planet or reasonable facsimile of thereof - image files for Mars and the Moon included), using your favorite bitmap. Some of the cool features:
- Multiple bitmap support. In Debian, upon installing both xplanet and xplanet-images packages, I was greeted by planet that was perfectly shaded to look like Earth at the moment - and on the night side, city lights could be seen. Oulu was the bright city in northern Finland. =)
- Cloud support. Generated, or taken from bitmap. Some people even use real weather data!
- By default, draws on the root window (in layman terms: pretty desktop background graphics). Also does windowed mode (spinning and freely rotatable!) and "virtual root" mode (in other words, fullscreen mode for xscreensaver or similar programs).
- Does different projections - no just 3D view and such, it also displays the map in different formats.
- Can also draw satellite locations (in case you want to be far away when ISS has a chance of crashing on your house)
- Also draws grids and places textual or graphical markers on specified locations (Just put coordinates to a file, and it displays that place!)
Home page: http://xplanet.sourceforge.net/ - also available as Debian package