Got this forwarded to me by a friend a couple days ago.
http://www.apple.com/downloads/macosx/math_science/osxplanet.htmlIt's a nifty little Freeware app that you can set up almost any way you want. Basically what it is, is a picture of the Earth as your desktop, which updates at a user-defined interval, and can update everything from Earthquakes, Volcano eruptions, Cloud Data, Satellite positions (just a few, mind you) and a few other things. The planet can be displayed an any number of ways (Azmuthal, Hemishpere, Mercader, etc)
You can tell it to stay focused on a certain geographic location (defined by latitude/longitude) so you can watch weather systems moving into and around your area, which you can set to be updated every minute. Pretty cool little app.
My one critique is that it hides its preferences button in the top of your screen with this inocuous little blue Earth icon, but once you find it everything is pretty straight forward.
Oh almost forgot, you can also view other planets in the Sol System, which is pretty nifty i think. Anyhow, check it out, it's free, so what do you have to lose?