Thanks to the staff at Blip.tv, audio-only versions of the PyCon 2009 talks are now available.
To download the audio for a talk, go to the individual page for the talk. Just below the license and summary information, there's a "Play episode as" select box. The choices are MPEG4 video, Flash video, and now MP3 audio. (For many talks, MP3 is listed twice in the select box; I don't know if these two choices are different in some way, or if it's a bug. I suspect a bug, because the RSS feeds only list one URL for audio/mpeg format.)
Want an easier way to download the audio? Wait for a few days; I'm working on scraping the list of talks and will add them to the PyCon podcast's feed.