If you are quick, it's only going to be there until end of tomorrow - 31st (US time I expect), there's a free track download at www.bobdylan.com - it's from the new album that's being released on April 28th.
I also came across this video today. It's a mashup of one of Bob's oldest recordings 'In My Time of Dyin' recorded in 1962 when I was 1 year old. Amazingly, the song was first recorded in 1927 under the title "Jesus Make Up My Dying Bed" by blues-gospel guitarist Blind Willie Johnson. Here it is given a really modern feel. I think its great.