@tedster great tip on the site search. I've mined that before for long tail terms and synonyms that I wasn't ranking for and then went after them. I've also used it simply for deciding what products to offer. If people are coming to your site and looking for products you don't have, think about offering them. If you can't offer them, instead of returning a "no results" page, put up a page with some decent info and some affiliate links to sites that do (or even "gasp" PPC ads for those products).