Mash-ups are so awesome. I love the idea of taking lyrics to one song and setting that to the tune of another song.  If I knew how to do this, I would try to do it all of the time. When you merge to totally different songs and put them together, it can create a different feeling and a different view point to the songs that you've never felt before. You may also be surprised about what songs actually go good together.
This was my entry for a contest on I wanted to test this out and see what it looked like when I put it on here.