Related Items plugin lets you relate a page, post or custom post type to other pages, posts and custom post types.
I do not like to write bad comments on free stuff, because I know all the needed hard work for that, and how it is time consuming.
This plugin does not work at all in my WordPress 3.8.1. Even the icons does not appear in page edit. I think things are missing in the code. I use Better WP Security and my theme, plugins,... are not located in /wp-content/ maybe my problems come from there.