All of the XML elements returned from Amazon are converted into variables for use in the script. There are many elements to list here; the best way to view them is to view Amazon's WSDL document. You can use any of those elements as variable by placing %% before and after the element name. The variables listed below are additional variables generated by the script from those results.
You can also use an apf command to display all available variables both those generated by the script and those that are taken directly from Amazon's XML. To display all variables put the following line in a page.template: <!--apf &apf_show_vars=ALL!!-->
page_templates - the overall page HTML (<head>, <meta>, <body>, etc.)
%%store%% - a more descriptive form of mode
%%subject%% - what was searched for or the browse category
%%header%% - either "store : subject" or the linked browse path (i.e. Bestsellers > store > subject) when applicable
%%in_association%% - the standard Amazon.com disclaimer
%%search_box%% - the search box
%%sort_box%% - the sort box
%%see_next%% - a link to the next page of results when applicable
%%see_prev%% - a link to the previous page of results when applicable
%%see_back%% - a javascript link to the previous page, works just like a browser's back button
%%see_index%% - for a "Google" style index of results pages
%%see_total%% - displays "page x of x" when there are multiple pages of results
%%shopping_cart_link%% - link to the shopping cart when applicable
%%products_html%% - the results wrapped in the HTML from the other templates (you MUST have this on the page template)
%%international_links%% - provides links to other locales
blended_templates - the HTML to display blended (All Products) results
%%blended_mode%% - the mode that the next results are for
%%blended_see_more_url%% - link to a more results for that mode
%%blended_mode_totalresults%% - total number of results for that mode
shopping_cart_templates - the HTML to display the shopping cart this is really complicated and you're asking for trouble if you change anything more than just the colors
%%script_name%% - the URL of the script
%%form_options%% - stuff from the URL, all the inputs you might be using
%%my_cart_item_price%% - product price * quantity
%%cart_qty_total%% - total quantity of all products
%%cart_price_total%% - oh, take a guess
%%continue_shopping%% - back button
%%checkout%% - button to transfer the shopping cart from AWS to a real Amazon shopping cart