Sorts any archive by any meta field.
<?php
$the_key = ''; // Field Name to sort on
$args = array( 'meta_key' => $the_key,
'orderby' => 'meta_value',
'order' => 'ASC'
);
global $wp_query;
query_posts(
array_merge(
$wp_query->query,
$args
)
);