Music mashups have been around since 2002 or so (the Nirvana/Beyonce mashup "Smells Like Booty" is the first one I remember), and video mashups for nearly as long. But I've never seen anything like what Kutiman is doing with his Thru You series of videos, taking upwards of 20 YouTube videos from as many different musicians and weaving them together into something completely unique and—and this is the most important thing—musically and visually compelling.
For some reason, though, he doesn't allow you to embed the videos in your blog, which seems to—ahem—contradict the spirit of the project itself. Still, it's amazing stuff. Check it out.
Update: Kutiman doesn't have the embed code on his page, but (duh) the clips are on YouTube. Here's the first one, "The Mother of All Funk Chords":