docbook2X is a software package that converts DocBook documents into the traditional Unix man page format and the GNU Texinfo format. It is free software under a MIT-style license. Notable features include table support for man pages, internationalization support, and easy customization of the output using XSLT. (Easy, because unlike other converters, the docbook2X stylesheets are written in a modular way, and the character escaping and whitespace issues with the man-page and Texinfo formats are encapsulated away from the user.)
WWW: http://docbook2x.sourceforge.net/