Information on the 8 planets, dwarf planets, and their moons.
If you want to be able to scroll through the solar system and see the comparison of sizes and distances of the planets, go to this website.
Check out this article about 2 planets sharing the same orbit in another solar system.
Here is a great program for viewing the night sky that students may be interested in playing around with. There are several of these type programs on the Internet if you do a search. The one that we have been looking at in 3rd grade, and will in 5th also, is Stellarium. It is available at Stellarium.org. It can be downloaded to Windows, Mac, and Linux.