Celestia, you can fly around to planets and stars, see orbits, etc. And each star or planet or whatever has a ton of information. Rod lectured us on luminosity. Galen let us know that Viga is the coolest moon of Neptune.
This presentation generated the best quote from barcamp stanford:
Audience: Hey Rod, what are those green lines?
5 year old kid: Those green lines? Those are curved space-time.
I could only lie there on the ground and whimper, that was so cool.
and the next best quote:
Galen: Can we see Uranus?