Watch for yourself.
Scrumdiddlyumptious (Willy Wonka Remix)
Bangarang (Hook Remix)
Carl Sagan - 'A Glorious Dawn' ft Stephen Hawking (Symphony of Science)
These already great videos work even better with yooouuutuuube, so give 'em a watch.
If you'd like to use your own video and share it in this thread then go to http://yooouuutuuube.com/ and go for it.
P.S. - I realize that this is old but I'm fairly certain most of you guys haven't seen it.
Everything You Do is a Balloon