Tenori - On: Crazy 21st Instrument from Yamaha.

This isn't the usual free online toy I feature, but I just needed to show you this beast. I need one now! The site says "Media artist Toshio Iwai and Yamaha have collaborated to design a new digital musical instrument for the 21st century, TENORI-ON. A 16x16 matrix of LED switches allows everyone to play music intuitively, creating a "visible music" interface."

Bit expensive though, Might try to make one one day, like the one aM lab made.

here.