Pretty cool toy - although it took me about a minute and a half to realize it was interactive. (not a bright boy).

Some other cool links that are (vaguely) related.

Music video / animation for Black Swan. I think it's just freehand.
http://www.youtube.com/watch?v=wepAxJ6BN30

John mayer doing a cover of Kid A - interesting video/animation but I don't know what kind of software was used to make it.
http://www.youtube.com/watch?v=qBMANXQqbTs

Not the least bit flash related, but here's Levi Weaver doing a cover of Idioteque. Just 1 guy and his loop machine.
http://www.youtube.com/watch?v=oK2LSITGQ6Q