you can influence the output of the tags widget (tag-cloud?) with some code in functions.php of your theme;
example:
add_filter('widget_tag_cloud_args','change_tag_cloud_args');
function change_tag_cloud_args($args) {
$args = array('orderby' => 'count', 'largest' => 25);
return $args;
}
for possible parameters, see http://codex.wordpress.org/Function_Reference/wp_tag_cloud
Thanks, I’ll check it out