Free MP3's at Amazon

Amazon was having a promotion over the holidays where if you purchased certain items you would receive credits towards MP3's or movies online. I ended up receiving $6.00 in credits for MP3's so while I was there today getting my music using my credits, I came across this page and it turns out several songs here are free anyway. I'm not sure how long these will be free, so I'd get them now if you want them. Amazon's free offerings seem to change from day to day.