I just stumbled upon the announcement for the Google Custom Search Engine. Based on Google Co-op, everyone can build his searchengine with the help of Google-technology. You can enter a list of URLs for example and let it search through all pages and subpages. If there are no hits, then there is always the possibility to use the normal Google-index as backfill which should then yield (hopefully) relevant results. I tried this for a few German SEO-blogs:
SEO-Blog Searchengine.