Bandmate Tuner (FREE) - Let's you see what note you're playing, and tunes you at the same time! 

Practice+ ($4.99) - Tuner, Metronome, Recorder, and More. This is what Mr. Hibbert uses every day!

GarageBand (FREE) - Lets you record, compose, and mess around to create your own music.

Vanido (FREE) - A singing coach that helps you train your eat and increase your range.

Noteflight (FREE) - A free music notation app that can be used in any web browser.

musescore (FREE) - A free music notation app that can be downloaded to your PC or Mac.