Looking only at British ones as the environment in the US is so different:
I subscribe to Plane Safety (although I didn't bother with the most recent one).
I found Flaps a bit tabloid for my taste and I got bored with Flying after listening to a lot (in fact just looking on iTunes he seems to have stopped anyway).
Royal Aeronautical Society releases some of its headquarters lectures as podcasts. I have enjoyed some of those although I no longer subscribe.
I also subscribe to Space Rocket History, Space Boffins and the Planetary Society podcasts although I think calling them aviation is stretching things a bit.
I am using subscribe in the iTunes sense of signing up for, not paying for!