You can use Amazon Web Services with the Rest method of just using HTTP Post requests and you will receive a XML response. Then use ns_xml to parse the xml with the ns_xml page and your pretty much there. I cache the results in the filesystem in both XML and my HTML Display of item versions.
You need to make sure to update the cache as needed though because Amazon doesnt want some data to become outdated.
If you or anyone else wants I can send the code that deals with the Amazon stuff, you would have to tweak for your
own use though. I offload some of the requests/processing to
a separate server to reduce load on the main user/frontend servers. Don't want to tie up your connection threads with lots of users potentially waiting for their requests to Amazon to be completed.
