A series of videos on YouTube are now making the rounds. A person named Kutiman used a whole assortment of videos from YouTube to create new songs. There's nothing completely new about it. People have been using audio loops for a long time to create music (I did that on the old Goatskin Pants theme song), and people have been mashing videos together for quite a while as well. I think it's the sheer quality that has people interested. It's a reminder that loops and mashups can actually be used to make decent music.
Here are my two favorites.
Mother of all Funk Chords
I am New
Kutiman provides links to all the originals so you can see where each part came from.