I subscribe to Russell Brand, whose schtick is getting a bit tired on TV but I like his podcast because he can interact with Matt Morgan, who's often funnier. Maybe that's where his TV stuff is going wrong; he needs a co-presenter of equal wit.
I also get the Best Of Moyles podcast, as I'm a fan of Chris Moyles' Radio 1 show. A lot of people like to diss him, but I think his stuff is entertaining and there's a good ensemble feel to the show. A great way to start the morning and the Best Of podcast allows me to catch-up on some bits I miss.
Also on Radio 1, the Scott Mills Daily is pretty good, although it's often frustratingly short sometimes, but still occassionally hilarious. I particularly like his phone pranks.
The Official Lost Podcast is great, once you get used to the oh-so-geeky Damon Lindelof and Carlton Cuse, who are undoubtedly great writers, but often wander into unfunny digressions. But this is an invaluable resource for Lost fans, particularly the Q&A session.
Battlestar Galactica Podcast. I'm quite new to this, subscribing for some insider thoughts on the stunning season 3 finale. I downloaded some from the archive, but to be honest I found them a little dry. Ronald D. Moore's stuff is usually the best, while budding writers will love the Writer's Room special... which basically has the writing staff chewing the fat over some season 2 episodes. Very illuminating about the creative process.
Mark Kermode's Film Reviews. This is probably my favourite podcast, as Simon Mayo and Mark Kermode's chemistry is great fun and Kermode's infamous rants are brilliant. I sometimes don't agree with his thoughts and he's a little too high-brow at times, but he also knows his stuff and has changed my opinion on a few things.
Scene Unseen Movie Reviews. I've only been subscribed for a few weeks, but I'm quite enjoying this podcast. Chris and Jimmy are two American movie-lovers who review films, but the "twist" is that one will see the movie, the other won't. It's very American, but interesting to see the fan perspective on stuff from across the pond -- particularly when discussing British stuff like the Bonds, Hot Fuzz, Shaun Of The Dead and The Wicker Man, etc.