The quick post interface adds a link next to the upload link on the publish and edit pages of EE. Click the link, a search box pops up. Add a title or keywords, select an amazon category, and get a list of results. You can select one of those results and have the asin, affiliate link and/or small image url added to a custom field.
Of course, you do have to specify the custom fields you want the amazon info going to first- see the installation instructions for details.
