Incredibox is a really cool way for kids to create their own beats and understand recording basics.
NY Philharmonic is a fantastic website that engages students through games about music.
San Francisco Symphony offers fun web based activities as well.
Musical Ancestries is a quarterly radio program with free detailed online resources designed to teach school aged children about world music. Each program focuses on a country or region, with accompanying Prezi presentation that include visuals, maps, audio clips, text and craft activities that students, parents and teachers can use to enhance their learning experience