WordPress' wpautop adds line breaks and empty paragraphs in some cases, especially when the first item in the post is an image. This attempts to strip those tags which may be desirable if you have special paragraph styling or have a consistently desired post format.

strip-empty-paragraphs.php

<?php

function remove_empty_p($content)
{
	$content = force_balance_tags($content);
	$return = preg_replace('#<p>\s*+(<br\s*/*>)?\s*</p>#i', '', $content);
	$return = preg_replace('~\s?<p>(\s|&nbsp;)+</p>\s?~', '', $return);
	return $return;
}
add_filter('the_content', 'remove_empty_p', 20, 1);

?>

This one works better, https://gist.github.com/ninnypants/1668216