I just love it. I work out pretty regularly, running, swimming, biking, some weights, some stretches, just a nice mix. And I listen to podcasts.
There is the NPR 'Wait, wait... don't tell me', some music podcasts and so on. But best of all is Itunes U: I just listened to the not very recent episode from Standford on Risk Management at Cisco "Managing Risk in an uncertain World" featuring Leslie Lamb.
I try to learn a interesting topics, which have a relation to my job (online marketing) but are not in my core area. And risk is important and interesting. At another time I listend to "why zebras don't get ulcer", algebra or how search engines work by some Google person.
I can really recommmend to try out the iTunesU part in iTunes! (Or search for itunes u site:.edu).
And for sure, as a professional I have to congratulate Apple to this move, this iTunes U program is excellent outreach and relationship building and managing.
The whole thing has one negative aspect ... if I listen to interesting stories and lectures, I don't work out as hard as when I listen to some nice beats....