Our friends at LoudWire have put together a very cool list of some must-hear genre-bending mash-ups.  The list is pretty good, including a few I have never heard before.  The one that jumped out at me as the coolest has got to be one that puts Nirvana's "Smells Like Teen Spirit" up against a young Michael Jackson's rendition of "Rockin' Robin"!  What do you think of this mash-up?!