I was poking around my Mac tonight when I remembered I once downloaded Stellarium, the GPL star chart. “Awesome” is the only way to describe Stellarium. It draws the night sky as seen from anywhere in the world. You can instantly find any object in the sky. It can even point a motorized telescope. I hope to take it in the back yard at night and get better acquainted with the night sky.
Also check out Celestia, another GPL space viewer, only Celestia lets you fly through space to visit an object up close and personal.
Hard to believe software like this is freely available. It is, though, thanks to the GPL.