This perhaps is one of the coolest things I've ever seen on YouTube... thanks Kim! http://blog.newsarama.com/2008/11/07/the-most-nerd-tastic-youtube-video-ever/
UPDATE: From TheDude:
it turns out that this kid did not actually write or record the song; he just lipsynched it. The kid wasn’t trying to fool anyone. He actually gives credit to the band on the actual YouTube page where he posted the video, but it’s just kind of a bummer to find out that there wasn’t some uber-genius child prodigy behind it. Anyway, the song is by an a cappella group called Moosebutter. Check out the update on this page: http://www.toplessrobot.com/2008/11/the_greatest_john_williams_tribute_of_all_time.php
Bummer, that takes all the fun out of it.