You won’t find this plug-in at WordPress for some reason and it’s a couple of years old but still works with version 2.71. Here’s what the author says:
Has your service provider complained you are using too many server resources? This could happen because you have a really popular blog or blogs (like Tricia) or it could happen if you have installed a poorly written plugin that’s a real CPU hog or it could be a combination of both! Regardless of the reason, you can continue to run your blog by paying more for a dedicated server, but that costs big money.
Fatal error: Call to undefined function st_related_posts() in /home/paulmyat/public_html/wp/wp-content/themes/WP565/single.php on line 22