If you like watching the stars on a warm summer night, you might enjoy Celestia and Stellarium.
Celestia allows you to wander through the Universe in three dimensions, from small scale objects such as the International Space Station orbiting Earth to our supercluster of galaxies. You can also download a lof of add-ons for Celestia (like the Space Shuttle or... the Millenium Falcon :) ).
Stellarium is your own private planetarium on your computer and is a great way to find objects (planets, stars, nebulaes) in the sky.
No need to be a rocket scientist to install and use them right away, they are pretty intuitive to use. Oh and they're both free :) These two great pieces of software give you a pretty good idea as to why astrophysicists can say there are more stars in the Universe than there are grains of sand on Earth...