Back in April I recommded the Mars Hill Audio journal. I have been pestering them by email, requesting they move to MP3 downloads, as well as tape and CD. Seems lots of people have and over the summer they began a downloadable version of their resources.
From their site: "MARS HILL AUDIO is committed to assisting Christians who desire to move from thoughtless consumption of contemporary culture to a vantage point of thoughtful engagement."
If you're looking for something thoughful and enaging for your ipod, give them a visit, this ranks as one of the best audio resources I have ever come across. If you want a taster there is a free 30 minute monthly podcast.