The thread on the PD documentation project seems to have died, and I presume that it is because no one is really sure how to go about it, or no one is willing to commit to actually steer it.
I am willing to put myself forward for some of the work, but as with anyone, my time is limited. Unless someone has a better idea, I would like to propose this following chain of actions.
documentation;
what outputs should the documentation be delivered as (HTML, RTF?, others?);
how should the documentation be indexed, markup'ed and stored (docbook? XML?)
what volumes/books/chapters should the documentation divided into [e.g.: book: PD chapter: pd syntax/principles (as per existing docs) chapter: object list (as per Max reference manual) book: GEM chapters... book: Source Code info chapter: how PD works chapter: how to compile PD subsection: how to solve the compilation problems in RH 7.x chapter: how to program externals book: specific subjects in PD (kind of like the Csound book) etc. ]
what existing documentation should be adapted/modified/recycled to fit in above
will supervise and adapt how the documentation is stored, modified, maintained, version'ed, etc.
reference
In a dream world, I would personally like to see a centrally maintained, always up-to-date, moderated on-line system, through which submissions can be made (with online forms, say); it would be beneficial to facilitate inline graphics (such as jpeg) for diagrams and screenshots; there should be automated links to object names and such; and there should be a way for people to annotate or add corrections online (and credit them of course.)
I have had a look at existing documentation projects and systems, and so far I haven't really found anything that does everything in one package. However it is obvious that XML should be the underlying format for storing the content of the documentation, although I don't see what the best way is to do that.