Automatic Box Generation by Category

I’m looking to monetize my site through Amazon Affiliates. The ideal, essentially, would be a box at the bottom of each post pointing to relevant books or movies. Which books or movies would be recommended would be determined and automatically added based on the category. I would manually enter from the Admin panel which books/movies map to which category and it would just have to display them nicely. Is there anything close to this ideal already available or would I be best off to try to create it from scratch? (I’m not very good with PHP yet so it would take a long time)