There was a posting to the docbook-apps list at Oasis about a standard word template where the styles map to a docbook element (even if not 1:1) so that only one stylesheet need be written to convert the output to Simplified Docbook.
Dan Gilleland replied that even though it's for Simplified, it can be extended to full DocBook. He posted the link to O'reilly's site, where you will find:
Microsoft Word for the PC or Mac, tagged according to our paragraph and character style template that is available at ftp://ftp.ora.com/pub/frame/templates/mswd/temp98.doc. Note that you should also be able to use this template for programs such as OpenOffice and StarOffice.
Thank you to Uratsuki for the link correction: ftp://ftp.ora.com/pub/frame/templates/mswd/.
I've got to try this in OO, and will report back...
See also: DocBook