I only have two that I listen to that haven't been mentioned yet.

Galactic Watercooler - It was originally Galactica Watercooler, but since BSG ended they've moved to discussing anything sci-fi, fantasy, and comic related. Each week they'll watch a movie, and then talk about it. Their tastes are pretty close to mine, and it's been a good way to find new stuff.

Home Theater Geeks - The first 10 or so episodes were really good, and really got me thinking in regards to my own home theater. The discussions haven't grabbed me lately like the first ones, so it's now on the bottom of my rotation.