Amazon has feeds of data for affiliates. You can create an entire store with those feeds. I'm using a script I wrote in ASP for our
Store. It's very easy to integrate into the content sections of your site as well. (In the following example, the code I'm using is VERY old and doesn't always show the most relevant results. Since I wrote the code, they've made it a lot easier to bring relevant results - I just haven't had time to update the code). Here's the
Google category of the directory and you'll see the listing of related products at the bottom of the page.
A WAY cool new feature they've added and that I have managed to update is the "text stream" search. I'm using it on our
Blog for the "Recommended Reading" list. In essence, I take the entire contents of the most recent entry in the blog and combine that with a list of general keywords that I made up to help tweak relevance. I put that paragraph of raw text and keywords (up to about 1500 characters) and send it to amazon. Amazon comes back with a list of relevant books. Way Good.
My examples, above, are in ASP. There is a whole set of PHP modules available for the service though. It's definitely worth looking into.
G.