NASA website lets you plan a space station viewing
My son and I just watched the International Space Station overhead. I don't think he quite understood what he was looking at, as he is only two-and-a-half, but he seemed intrigued by the idea that there were people on that little shiny speck. I thought I would share the experience with all my fellow Parenthackers. If you want to view it yourself, just head over to: http://spaceflight.nasa.gov/realdata/sightings/index.html and plug in your address. It will tell you when the next good time to see it will be.
I love this idea. You never know which moment or experience will spark a child's wonder about the universe. I know I never looked at the sky the same way again after reading The Little Prince. Another short, lovely picture book that gets kids thinking about the vastness of time and space: The Jupiter Stone.