I am a Fitness Rock charter member and I used Podcast for Running. Started my running program and ran more than I ever had in my life but running really aggravated the arthritis in my neck.

Love Fitness Rocks.

This may not be for everyone but there is a website DharmaSeed.org and some of the free talks are very "centering" and I believe quite helpful. They download directly into my iPhone for a listen. It seems to use Quick Player so they would probably download into iTunes to put on an iPod. You can search the talks (mindfulness, uncomfortable emotions, lovingkindness, etc.) to get a topic you're interested in.