This Related Posts Plugin for WordPress displays links to a given number of Posts that are related to the current post(s) by Tags or Categories. It can Automatically add links to Related Posts at the bottom of every Post or you can drop the Widget on your sidebar.
Settings: Excluding posts, categories, and tags; section heading; number of links; display post date; and excerpts.

EZ Related Posts Footer Links and Widget

Display a linked list of related Posts by Tags or Categories at the bottom of every post or on the sidebar. Options to show Post Date and Excerpts.

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 …

EZ Related Posts Footer Links and Widget vs Ozh' Better Feed