Connect and Collaborate With NASA. Connect and Collaborate With NASA is a page linking to all of NASA's iOS, Android, and Windows Mobile apps. The page includes apps that I've previously tried Spacecraft 3D (my review) and Sector 33 (my review) as well as some new-to-me apps like Comet Quest (free iOS app) and Be A Martian (Android).
Applications for Education
If you're looking for some free apps to support your lessons in engineering and science, take a look at Connect and Collaborate With NASA before you jump to searching in the Google Play or App Store. Some of the apps that I recommend starting with are Planet Quest, the Lunar Rover Simulator, and Earth as Art. All three of those apps are available through Connect and Collaborate With NASA.