Tons of good podcasts in iTunes for free.
Some of the ones I've listened to are:
1. University of Arizona 7 podcasts on climate change (very good, things you won't hear from the media, & cutting edge research on it).
2. Fortress Draconis (Eragon type book read by the author).
3. Lots of "How To" books:
Mr Manners Quick & Dirty Tips for a More Polite Life
Learn Spanish - Survival Guide
4. Astronomy a Go Go (monthly podcast on the Heavens)
Discovery channel, National Geographic, History channel, New York Times, the Weather Channel, etc all have free podcasts.
From the Search in iTunes type in a genre you are interested in, ie: cycling. You will get a list of all things regarding it. Then choose "Podcasts" from the top menu & you will get all the podcasts on Cycling.
Audible.com also has audiobooks on iTunes, but I found audible.com to be VERY expensive (& unnecessary with all the good podcasts now).