Chris Chiasson has created custom Google search engines for the DocBook-apps mailing list archives and the DocBook Official Documentation (including Norm's "DocBook:The Definitive Guide" and Bob's "DocBook XSL: The Complete Guide").
David Cramer then took them a step further and created Firefox search plugins for these pages! The plugins are available here: http://www.thingbag.net/docbook/. Very cool! Thanks guys!