Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
You can listen to music while you do other stuff, as long as it isn't a 3rd party app like Pandora.
 
I wonder if everyone would still scream about multitasking if Pandora was allowed in the background. Seem's like the iPhone always saves your place when you switch apps, so you don't have to really worry about losing your work. Plus push notifications work great for AIM and other things.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.