Aaron D. Campbell

This plugin allows you to manually enter links that are related to a post. They 
can be on any site and you can enter just the URL or an entire link (specifying 
the title attribute, onclicks, etc). There are helper functions to display them 
in your theme or you can simply tell the plugin to automatically add them to 
posts or even just single posts. The list is output as an unordered list (ul) 
with an optional title, and everything has CSS classes to make styling easy. 
Requires PHP5.

Manual Related Links

A related links plugin that allows you to manually specify links, even if they're on another site. Requires PHP5.

Your feed, on steroids : add a custom footer to RSS items with, for example, a copyright notice, a “Read More (400 words)” links, an “Add to del.icio.us” link, a list of related entries, or anything really (even custom PHP functions). Compatible with Feedburner or similar services.
Improve connectivity between your feed and your site !!
For documentation and tips, please refer to the official plugin page for <a href="http://planetozh.com/blog/my-projects/wordpress-plugin-better-feed-rss/" title="Better Feed" rel="nofollow ugc">Better Feed</a>

Ozh' Better Feed

Your feed, on steroids : add a custom footer to RSS items with, for example, a copyright notice, a "Read More (400 words)" links, an "A …

Manual Related Links vs Ozh' Better Feed