My favorite Catholic podcast is Joan Lewis' 'Vatican Insider'.
As I mentioned in my EWTN Radio review, Joan is EWTN's Rome bureau chief. In addition to calling into Teresa Tomeo's show on Wednesdays, Joan has her own radio show which is on Saturdays.
It is a half-hour show, but she seems to fit alot into it.
She starts out with a news update, she has a question-and-answer segment where she answers email questions, and she has an interview segment where she interviews someone. It is a very informative show/podcast.
I usually don't get to listen to it on Saturdays, so I download the MP3 weekly, and listen when I can.
Here is Joan's blog.
Here is EWTN's podcast page where you can get Vatican Insider, as well as MP3's of many of EWTN's programs,