I've set up my iTunes to download to Dropbox and now I have my podcasts saving to a dropbox folder. I have subscribed to the the folders event feed and it gives me links to download the mp3 files but I want it to display like a podcast feed so my podcatcher recognizes the mp3 as a media enclosure and downloads it automatically.
It doesn't seem that the XML is formatted correctly to be picked up by podcaster. There doesn't appear to be a way of formatting the xml on the site through preferences so unless you use the developer API and write something I don't think you can reformat it.
Also Dropbox isn't really setup as a hosting service so if you have a free account, they tend to throttle heavy usage:
help docs look for #45
hope that helps