Tools to make DocBook easier

[Warren Block <wblock@wonkity.com>]

What tools are there to make working with DocBook easier?  I wrote a 
lint-like proofreading tool called "igor" that looks for common 
mistakes: http://www.wonkity.com/~wblock/igor/
Presentation: https://www.youtube.com/watch?v=-9MLREFzdR0

It occurred to me that the text "styles" settings of GUI word processors 
could be used to make DocBook markup easier.  There is an OpenOffice 
page that talks about this, but does not really give a working example: 
http://www.openoffice.org/xml/xmerge/docbook/UserGuide.html

What other tools are there to make writing or rendering DocBook easier?