He's always been a Dylan fan. He wrote Blood Money for Dylan (take a look at the sleeve notes). As far as I know he has been a U2 fan since the early 80's, a big Elton John fan (apparently Jon said that in the 70's he made a mock up of Eltons Yellow Brick Road for a school project such was his admiration for Elton) and a big Tom Waits fan as well as Elvis, Petty and Bruce.

Have to be fair, Jon has decent taste in music.