Custom Field Finder is a WordPress plugin by Joost de Valk that allows you to easily find the custom fields (including hidden custom fields) and their values for a post, page or custom post type post.
Go to Tools -> Custom Field Finder, enter the post ID of any post and you’ll see all the custom fields, including the ones that start with an underscore ( _ ) that are normally hidden from the custom fields interface.
Download: http://wordpress.org/extend/plugins/custom-field-finder/
Shows some sample plugin output.
