Yesterday we announced draft-gregorio-atompub-multipart-00. By "we" I mean Google, and by "announced" I mean that the internet-draft got published last month and I finally got around to writing a blog post this week. As usual the discussion should take place on the atom-protocol mailing list.
One thing I didn't mention in the announcement is that the source for the draft is hosted on Google Code Project Hosting. Not only does that give me Subversion, and the ability to host files ( like the HTML version of the spec), but also the Issue Tracker which I will use to track open issues with the spec.