I think to really do it right we would need to implement a podcast feature or extend the functionality of the blog to support it. Maybe we just need to add a field in the db for an optional mp3 file (or url to one) for each blog post. I've made a note to remind myself to look into it when I get a chance. Its a really good idea.
Would be good to clarify the needed features. Is a separate audio feed really needed? I thought they just embed links to the audio. Like Odiogo, just consumes my mojoportal blog feed and adds their text to speech generated mp3 into an output feed. So the only difference is we would have the option to use our own produced mp3. What other features does it need to be considered a podcasting blog? A widget to play the podcast, an upload mechanism for uploading the mp3. What else?