I wanted to build some search engine friendly minisite with amazon XML feeds. Basically you choose a keyword and get results, eventually you get links to other keywords, all works recursively and so on. First of all, after I logged in into my amazon associates account I couldn't find anything good. I remember that when I was using mediaplazza feeds or peakclick feeds, everything was easy due to good and straight documentation. I couldn't find anything like this on amazon. I searched 3rd parties and found these which are pretty helpful: http://www.chipdir.nl/amazon/ and http://smallplanetonline.com/aws.php. They come with sources but anyway, instead of using those I preffered to write everything from scratch. I just look into how a query to http://xml.amazon.com/onca/xml3? should look like and then I played with the parameters and parsed everything using xml_parser function and with help of the examples from http://de.php.net/manual/en/function.xml-parser-create.php.
I just wish amazon could offer some good documentation and eventually some kind of simulator for the queries. But maybe they do but I was just too ignorant to see or they know where to hide it well. I got so pissed searching and I started to feel like I was waisting time and decided to do my own code.