The three best podcast in order in my opinion are:
1. Ask about Fly Fishing Internet Radio
Fly Fishing - Internet Radio
2. The Orvis Fly Fishing Guide Podcast
Fly Fishing Podcasts | Weekly Fly Fishing Podcast Tips | Orvis Fishing Podcasts | Fly Fishing Tips W
3. The Itinerant Angler Podcast
The Itinerant Angler
I have listened to ALL of Harry Murray's Podcasts and the early ones have some value, but in my opinion they have become an advertisement for his flies and shop. He always says the best fly for any situation is some version his Mr. Rapidan flies. So start with his introductory podcasts.
Unfortunately, some of the very best podcasts from Fly Fish Radio are no longer available. Norm Albiston's 4 podcasts on fly fishing are classics.