In celebration of Willie Nelson's 80th birthday Tuesday, U2 posted a video on their website -- U2.com -- of them performing "Slow Dancing" with Willie. Bono wrote the song for Nelson and the clip they posted is never before seen footage made by filmmaker Lian Lunson. And they posted a note to Willie that reads, "Happy Birthday, Willie! 80 and still a pilgrim. All the best… Bono, The Edge, Adam & Larry."