WpRecipes.com - Daily recipes to cook with WordPress

To create the shortcode, simply open your functions.php file and paste the shortcode function:

function related_posts_shortcode( $atts ) {
	extract(shortcode_atts(array(
	    'limit' => '5',
	), $atts));

	global $wpdb, $post, $table_prefix;

	if ($post->ID) {
		$retval = '<ul>';
 		// Get tags
		$tags = wp_get_post_tags($post->ID);
		$tagsarray = array();
		foreach ($tags as $tag) {
			$tagsarray[] = $tag->term_id;
		}
		$tagslist = implode(',', $tagsarray);

		// Do the query
		$q = "SELECT p.*, count(tr.object_id) as count
			FROM $wpdb->term_taxonomy AS tt, $wpdb->term_relationships AS tr, $wpdb->posts AS p WHERE tt.taxonomy ='post_tag' AND tt.term_taxonomy_id = tr.term_taxonomy_id AND tr.object_id  = p.ID AND tt.term_id IN ($tagslist) AND p.ID != $post->ID
				AND p.post_status = 'publish'
				AND p.post_date_gmt < NOW()
 			GROUP BY tr.object_id
			ORDER BY count DESC, p.post_date_gmt DESC
			LIMIT $limit;";

		$related = $wpdb->get_results($q);
 		if ( $related ) {
			foreach($related as $r) {
				$retval .= '
	<li><a title="'.wptexturize($r->post_title).'" href="'.get_permalink($r->ID).'">'.wptexturize($r->post_title).'</a></li>
';
			}
		} else {
			$retval .= '
	<li>No related posts found</li>
';
		}
		$retval .= '</ul>
';
		return $retval;
	}
	return;
}
add_shortcode('related_posts', 'related_posts_shortcode');

Once done, you can use the following shortcode in your posts to display the related content:

[related_posts]

Thanks to Blue Anvil for this awesome shortcode!