Official DocBook home
DocBook reference documentation and schema repository
XSL and DSSSL stylesheets
DocBook XSL: The Complete Guide – everything you need to know about using and customizing XSL stylesheets
DocBook V5.0: The Transition Guide—how to migrate from DocBook V4.x to V5.0
These slides: http://www.kosek.cz/xml/2005warpstockeu/