Microsoft Songsmith

So Microsoft put out this program called Songsmith, which I imagine is supposed to compete with Apple's GarageBand on some level. Among other features, it has the ability to create backing instrument tracks for vocal recordings. Of course, the Internet had commandeered Songsmith for comedic purposes. Now you can listen to your favourite tracks remixed into different genres (and sometimes even different time signatures)! Some of "the best" are listed on this post, but if you click around on Youtube's suggestions, you'll find a ton more.

http://www.techcrunch.com/2009/01/31/so-bad-it-hurts-classic-hits-by-microsoft-songsmith/