I have a client for whom we have purchased Google Site Search. It works well for HTML pages served by the CMS, but files aren't being reliably indexed.
I wrote a script to generate an XML feed (sitemap) of all the files in the CMS which I've plugged in to Google Webmaster Tools for the site. It says that for that sitemap 923 URLs have been submitted, but only 26 have been indexed.
The client relies heavily on searching within files, which is why we decided to use Google search, so this is a bit of a problem.
Many of the files aren't linked to from any page on the site, as they are old and therefore don't merit having a page of their own. But they still need to be accessible through search for archiving purposes.
The file archive XML can be found at www.sniffer.org.uk/file-archive and the standard XML sitemap (of pages) can be found at www.sniffer.org.uk/sitemap.xml.