I tried Google custom search for my updated site but I was unhappy with the control I had over what got indexed, so I decided to implement my own.
A quick search revealed the awesome Whoosh search library. It is very well documented and super easy to use.
I wrote a 50-line python script (buildIndex.py) to walk the _site directory and index the generated html files. It would be cool to integrate this into the Blogofile build process as a filter but I knew I could get a separate indexer going quicker.
I'm very satisfied with the result and the ease of getting it going. I simply added the buildIndex script to my Post-Receive Service Hook for automatically updating the site when I push to github. It takes about 15 seconds to index my 350 pages. Searches take milliseconds.