I recently found this series of musical mash-ups by someone called Kutiman.
Each song is created from a number of YouTube clips, normally of people playing instruments or singing at home on their web cams. These are spliced and mixed together to create new tracks.
There are a range of songs on the his ThruYou site or via YouTube that cover a range of musical styles including Funk and Hip-Hop.
The whole ThruYou project shows what is possible when you don’t have to worry about Copyright restrictions. Had this series of mash-ups been made from music of artists under Big Media contracts the ThruYou site would have been closed down under the massive weight of legal threats in very short time!