dcannon1

Small, lightweight (under 7k) widget that shows posts from the same category as the current post. Several options for customization along with numerous ordering criteria for posts. Displayed only on single post pages. Based on Related Links by Category by Andrew Stephens
Options
<ul>
<li>Title – Set the title of the widget (or leave blank)</li>
<li>Number of Posts to Show – Set how many posts are listed in the widget</li>
<li>Order By – Choose how the related posts will be ordered (including random posts)</li>
<li>Show Category Names – Toggle whether category names are displayed above groups of posts</li>
<li>Link Cat Name to Archive – If category names are being shown, choose to have them link to the category archive page for that category</li>
<li>List Posts Multiple Times? – If a post is classified under multiple categories use this toggle to determine if it will be shown under each category, or only under the first category it shares with the current post. This should be set to no if you are not displaying the category names</li>
</ul>

Edward R. Jenkins

Nifty Related Posts adds related posts by category to the bottom of your post template. Includes options for thumbnail size and alignment, excerpt length, related posts per page, and more. Minimal styling and disable CSS option to fit with your theme.

Nifty Related Posts

A WordPress plugin that adds related posts by category to the bottom of your single post template.

Related Posts by Category Widget vs Nifty Related Posts