Just Related is a simple plugin to display related posts below your post. Related posts will appear as a list of titles.
You have no need to take any extra stress to handle this tiny plugin. Just install and forget.
In this primary issue of Just Related you will get 5 related posts just below your posts.
<h4>Feature:</h4>
<ol>
<li>Easy to Maintain</li>
<li>Light for WordPress</li>
<li>Auto Configuration</li>
</ol>

Just Related

Just Related is a simple plugin to display related posts below your post. Related posts will appear as a list of titles.

Shambhu Patnaik

Pro Related Post Widget plugin.dynamically show related post according to post.
Note:
<ul>
<li>unchecked (Hide if no posts to show:?) case.if no post found then it work as latest post.</li>
</ul>
More Detail : http://socialcms.wordpress.com/

Pro Related Post Widget

Pro Related Post Widget plugin.dynamically show  related  post according to post.

Just Related vs Pro Related Post Widget