I mostly try to avoid running with music. I always seem to want to match the tempo of the song, which isn't necessarily the rate I should be running at a given moment. The exception is when I do speed work, when I find the music gives me the boost I need to get through tough intervals.
But today, for a 5.5 mile recovery run, I decided to go ahead and listen to a song I've been enjoying a lot lately, Girl Talk's All Day (fun music—more of an 80's/90's pop/hip-hop mix tape than a true song). It's 71 minutes long; I had started it at the end of yesterday's hill workout, and I wanted to finish it. The goal was to run 10-minute miles, something I always find a little difficult; it's quite slow for me, but that's the point of a recovery run. For the first 4 miles, listening to music, I didn't quite make it -- I averaged about 9:30 per mile, even on the uphill segments. Then, when All Day ended, about halfway through Mile 5, I switched to a podcast. Instantly my pace slowed, and my pace for the last two legs was 9:56 and 10:03, just where I wanted to be.
I don't wear an iPod when I race for similar reasons: I find the music distracts me from running the pace I want to. Podcasts distract me too, in a different way: they might actually slow me down a bit, which is probably good for anything other than tempo runs and speed work. My tempo runs are generally done in a group, so I'm not listening to the iPod then either. But I know many people really struggle to run without music. Marc Hirschfield, in his entertaining summary of the Disney Marathon, talks about his iPod breaking down as nearly as big a tragedy as a knee injury.
Tomorrow I'm getting up at 3:30 to run the Fellowship of the Idiots. I'll be leaving my iPod at home.