The Cool thing we did here was make a pop-up of the universe. You can find directions here. Essentially the sun pop's up then the planets are attatches with a bit of wire so that as the lap book opens they hover around the sun...(boy did the boys love doing this!)
k - I promised I'd give y'all the printables and links for our solar system lapbook...so..."Ta-Da!"
NASA's "Our Very Own Star: The Sun" this is actually a little book you can print!
Planets Coloring Page
Various Printables (there is actually a very good small coloring book I used for my preschooler, while my older son did the harder stuff!)
Moon Phases (action flipbook)
Live & Learn Press Lapbook
Solar System Printables (these are the more advanced word finds and such)