Personally, I find the best program that I've come across lately to be Celestia. It's a low-resource
3-D rendering of the known universe, allowing you to zoom in and trace not only the paths of the space shuttle, ISS, Cassini, and other man-made
objects, but to zoom out to the farthest reaches of our known Galactic neighborhood.
The program itself is rather small, and there are a ton of add-on available for it all free of charge under open-source. You can also run scripts with
it, making it a research tool as well as neat toy for those interested in really coming to grips with where we are in the universe.