For podcasts I would recommend a podcatcher, I have used both Doggcatcher and Pocket casts, both are very good, I personally like doggcatcher a little more than pocket casts. The problem with most audio only players is they will not update RSS feeds while podcatchers will.
I am still looking for a good audiobook player, podiobooks are great but I've got a couple giant files that need a real audio player, may try Mort audiobook player