I know of several interactive websites for Music Theory.
I really like the teoria website. It not only has lessons, but interactive questions and practice drills. It is a great resource for student practice in ear training.
The apps that I found for use with Music Theory are:
- Karajan Beginner
- Wivi Band
They are not that powerful and some are only available on the iPhone. Of course there are also apps for tuning and metronome which would be useful. Right now I have computer software that is more powerful for Music Theory and it is designed with the AP Music Theory test in mind. It provides for practice as well as testing. Hopefully in the future they will develop an app to use in conjunction with the software. It was the capability of recording individual test scores.
I can see us using the iPads as actual "sheet music" in the future. With a central controlling station, the iPads could be sync'd and music downloaded to individual iPads. This would give us enormous flexibility. We could perform a piece in a given key and with the click of a button change the key for everyone instantly. You could also easily rewrite an instrument's part so that it played something else simply by cutting and pasting.