Looks like some astronauts get bored when they go a-flying above our heads, so they need some music to kill time.
Look closely on the picture below, taken probably from one of Endeavour's mechanical arms or an astronaut:
Yes, it's a (3G I think) iPod in there...
(via Engadget)
[update: I stand corrected by Xavier who, in the comments, points out it's a 4G iPod.]
