WordPress: sort by post view
http://subharanjan.com/how-to-display-wordpress-posts-sorted-by-post-view-count-solved-without-a-plugin/
<?php
$args = array(
'orderby' => 'meta_value',
'meta_key' => 'post_views_count',
'order' => 'DESC',
'post_status' => 'publish'
);
$ranking = 0;
?>
<?php query_posts($args); ?>
<?php if ( have_posts() ) : ?>
<?php while ( have_posts()) : the_post(); $ranking++; ?>
<!-- HTML -->
<?php endwhile; endif; wp_reset_query(); ?>