Space by THIX: Make Your Own Solar System

Space by THIX is a great app that allows you to create your own solar system and add anything from a black hole to a terrestrial planet.

Chemist: A Lab on Your iPad

Chemist is an app by THIX which is a virtual chemistry lab on your iPad. It's great for doing serious experiments, and also mucking around in and seeing what happens when you react one chemical with another.