Flowkey - The easiest way to learn piano with your iPhone or iPad
Synthesia - A fun way to learn how to play the piano.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
Linthesia - Linthesia is a game. A game of playing music! You only need a MIDI file
Piano Lessons - Piano Lessons is one of the reliable libraries of online piano lessons provided by world-class instructors, making you learn or practice with the musical instrument without any hassle.
Piano From Above - Piano From Above is a program that turns learning the piano into a videogame.