Despite the usefulness of the Q&A format, I still think a Wiki would be a good place to document v7, like a book. Sometimes, I'd like to just read about a topic. The contents of the wiki could be put into documentation or training materials.
There maybe some individual or team at OpenERP currently working on a book but I think the need for it is now and the community would be willing to get started on it right away if they were given access, like a wiki.
Possible duplicate: http://help.openerp.com/question/1313/is-there-a-place-where-we-can-post-guides-for-openerp/