Hi, I've just added client and server support for AtomPub-multipart media creation. It follow the Joe Gregorio specification draft:
http://atompub-mulitpart-spec.googlecode.com/svn/trunk/draft-gregorio-atompub-multipart-02.txt You can see how to configure it into the wiki: http://cwiki.apache.org/confluence/display/ABDERA/Support+for+AtomPub-multipart
