According to Future Tense Podcast there are now two organizations that have recently started up to help define how future advertising should be integrated into downloaded media like audio and video podcasts.
The groups are:
There are some interesting related comments from Eric Rice and Podcast Brothers. I think the concept is good and something that should be monitored for those interested in taking advertising for their new media content.
There is also a very interesting thread related to this topic called "How To For New Media Makers" that has some interesting ideas worth digging into.