Interactive Music: Three different ways to explore and interact with the science, sounds, and joy of music. Children can compose, explore instruments, and learn to read basic notes and music.
Music on Khan Academy: Tons of tutorial videos are organized to give you an amazing introduction into the world of music. Explore the basics of math in music, musical masterpieces, and the instruments of the orchestra.
Incredibox: Enjoyed by music teachers, Icredibox is used in schools to introduce rhythm and music mechanisms to children in an fun, creative, and modern way.
The World of Music: The San Francisco Symphony created this interactive musical world for children to explore and discover new learning related to music. The unique game-like interface really grabs kids attention in a way similar to modern video games.
Patatap: Creativity unleashed. Integrates with keyboarding in the most musically creative of ways.
Exploratorium Music: This California based online science museum explores the links between music and science. Lots of ways to explore and create.