JGE Automatic Content Generator is a PHP script that will automatically add relevant content to existing web pages. Uses Calais to perform semantic analysis of an existing page's content to find essential keywords and then pull content relevant to these keywords from Freebase.
Did you think the search engine wars were over, and Google won? New kid on the block Blekko, currently in closed private beta, urges you to reconsider. Once out, it's bound to become the favorite of search refiners, with the results likely made available as an API.