MT-RefSearch
Eliot Landrum made a post to the Movable Type forums about his MT-RefSearch add-on for a PHP/MySQL-powered Movable Type blog... like mine! Basically it's a PHP file you suck into your page and it automatically determines (based on referral URL) whether the visitor is coming to your site from a search engine like Google. If they are, then it does a query on your blog (directly from the database) and shows up to 5 results. Pretty spiffy I must say.