We use a WordPress plugin called Amazon Showcase WordPress Plugin to put books from Amazon on some of our client's sites. Well, we used to, until recently.
This plugin produces ridiculously long Amazon links for Amazon Affiliate Program (which let's you make money advertising Amazon products):
There are parts of this long URL which seem to be pretty easy to understand and they seem important and there are some part which seem to be redundant.
Check out our tool here:
Other thing which bugs us about the Amazon Showcase WordPress Plugin is that it's not caching the images. The images are always loading from Amazon servers - slowing down your page load.
That's why we are working on our own Amazon plugin which we may release on wordpress.com when it's ready (it will have nice URLs and will store the images locally, among other cool features).