Did a search and found a nifty plugin for making enclosures in feeds for MT.
To start audio blogging, you have to do the hard part first — record the audio file. Be interesting. Let’s say you recorded as an MP3 file. Then upload the MP3 file to your web server so that it is available for download. Then create a new blog entry that announces your post and has a link to the MP3. The link should be a standard tag with the HREF pointing to the MP3. Save and rebuild your index files. Your RSS 2.0 index will now have an tag in it pointing to the MP3. You are all done!
Brandon Fuller | MT-Enclosures: A Movable Type Plugin
Hope I find the time to play with podcasting soon.