Here's the super-secret password for the clubhouse.
In the search box on the main amazon.com page, there's a drop-down list on the left hand side of the text entry. Click that and change it to "Books". Now just hit search (you can leave the text field blank). That will bring up a search results screen with a bunch of filter groups on the left. Scroll down and select "Kindle Edition" under "Format". After the page reloads, scroll down even further and you'll have a checkbox for "Prime Eligible". Select that, and you'll have only the books you can rent with Prime. You can then further refine by genre, search term, whatever.
In the search box on the main amazon.com page, there's a drop-down list on the left hand side of the text entry. Click that and change it to "Books". Now just hit search (you can leave the text field blank). That will bring up a search results screen with a bunch of filter groups on the left. Scroll down and select "Kindle Edition" under "Format". After the page reloads, scroll down even further and you'll have a checkbox for "Prime Eligible". Select that, and you'll have only the books you can rent with Prime. You can then further refine by genre, search term, whatever.
The selection is generally pretty awful though.