The VirtueMart Project holds its Documentation (User and Developer Manual) in the DocBook XML Format. The Advantage of this: we can distribute the Manuals in various Formats (html, pdf, chm) and quickly re-create a Manual when something has changed.
Recently we found that it would be good if Users could quickly find the right Page in the HTML version of the User Manual. There are various ways to make static HTML Pages searchable - but the "Google Custom Search" seemed to be the best and easiest solution. It allowed us to create a new custom "Search Engine" - only for the User Manual - and it works! The HTML Code for the Search Box was integrated into the custom DocBook XSL, which creates the HTML Version of the User Manual - and voilà:
The online User Manual for VirtueMart 1.1 now is searchable!