I think it's safe to say that Podcasting is a kind of useful application of RSS to simplify the repetitive task of downloading periodic audio programs. With that in mind, Podcasting clients like iPodder could really add some utility with audio post-processing. Here are some things I'm thinking of:
1. Split large MP3's into smaller files for players that don't bookmark or fast-forward slowly. I previously posted some information on how to split DotNet Rocks MP3's with mp3splt). I'd like Podcasting client to automate this. It should be configurable, but at a minimum should let me say "split into 2 minute chunks" or "split into "10 minute chunks", etc.
2. Time Compression - a lot of people have rejected Podcasts because it takes too long to listen through them to compared to the amount of information you receive. In WMP I usually turn the speed tup to about 2x and still get bored sometimes, but most MP3 portables probably don't allow speeding up the play speed. Podcast clients run in the background on powerful modern computers, though, so they should have no problem re-encoding the audio a higher speed I get to pick.
3. Add background music - during my commute, I regularly flip between music and spoken word (books on tape, NPR, talk radio, or Podcastable content like DotNet Rocks). There's no reason the two couldn't be mixed together. I could pick a folder or list of music MP3's that would make good background music, and my Podcasting client could mix them together. Then I'd get to hear my music and get my content.
4. Recommend similar feeds - It's hard to find good content now. iPodder.org has a Podcast directory, but it's not very useful. Assuming the content selection continues to grow (and it had better or this whole thing is going down like Boba Fett), they need a webservice that recommends feeds based on the ones I've subscribed to (yes, the aluminum foil hat crowd would need an option to shut this off).
 The astute reader will note that this has nothing to do with audio post-processing. Yeah, well it was one other random feature idea and I thought I could slip it by here.