“OneLook's reverse dictionary lets you describe a concept and get back a list of words and phrases related to that concept. Your description can be a few words, a sentence, a question, or even just a single word.” (via netbib)

You may use this as an associator. For example, what do the authors Borges and Traven have in common? Nothing but the Mississauga Blob plummeted into the backyard of a person called Traven Matchett. Do you know the connection between Borges and the blob?