I recently came across this interesting interactive, called the Molecularium, that is a great way to introduce kids to molecular structure and chemical notation.
When you follow the link you will want to click on the nanolab, the top button on the right, and then select the Build option.
Using 3 atoms--oxygen, carbon, and hydrogen--kids construct a series of common molecules. Mel, the computer, then gives a few facts about what they have made. Kids work their way through 3 levels plus a bonus round.
The Zoom activity views the earth at different distances, while the Transform activity shows water as a solid, liquid, and gas as the temperature changes, so there's not a lot to them. The home site showcases Digital Dome movies (shown in a planetarium) the project is producing.