I subscribe to only audio podcasts since I'm limited to a Nano at the moment, but these are the audio ones I listen to regularly:
Book Panel with Simon Mayo - Simon and 2-3 readers review a couple of newly published books each week, and often have the authors in on the discussion
Daily Mayo - Simon Mayo again (he's a fantastic host/interviewer) - interviews with authors to politicians to film stars
KCRW's The Treatment - Elvis Mitchell is one of the best interviewers I've ever heard
Mark Kermode film reviews (of course!)
NPR: Movies
NPR: Fresh Air
This American Life
The Observer Film Weekly - UK podcast, reviews current releases and often has interviews with actors/directors
The Film Programme - another UK film podcast
Slate's Spoiler Specials - Slate's film critic Dana Stevens talks over a film with a guest
Watching the Directors - nice, long (1+ hour) conversations featuring various directors and their bodies of work
White Horse Inn - theology talks broadcast from my husband's alma mater
NPR: Car Talk's Call of the Week