Paul Youlten writes “StoryCode extracts the narrative structure of novels and uses this information to recommend new books to readers. Only 1030 books have been coded so far (May 8 2005) so some of the recommendations are a bit “left-field” but you can add your own codes to the system to make it better.”
This looks like a lot of fun and interesting! I am assuming it is free and hope to get some time to play around with it.
AllScifi
has a book and movie search function for themes. Pretty nifty.