WeatherBug Elite - A great many iPhone and Touch users I know have the free version of WeatherBug installed on their device. I did too, for a long time and then a few weeks ago I upgraded to WeatherBug Elite, which eliminates ads and provides additional features.
iPhone and iPad apps tagged "educational tool."
Soar Through Space with a Pocket Planetarium
Planetarium is an iPhone app that puts the solar system in your pocket. Developed by Core Coders, Planetarium features planets displayed in beautiful 3D along with features that allow you to fly across the solar system or watch the rotational orbit of the planets.
Harp is Good for Education, Not For Fun
Harp – The Harp App has just been released! After a long-awaited arrival, this musical iPhone app features a sweep-touch virtual harp with 14 chord structures in any of the 12 keys. This equates to a total of 168 unique chords.