We've using Google App Engine and their Text Search feature (https://developers.google.com/appengine/docs/python/search/overview https://developers.google.com/a

We've using Google App Engine and their Text Search feature (https://developers.google.com/appengine/docs/python/search/overview https://developers.google.com/appengine/docs/python/search/o...). It's still experimental and slightly buggy but very easy to use and obviously scales well. They haven't announced pricing for the service yet which is quite key since search is our main feature.