AWPCommentReply

function awordpress_load_scripts($hook) {
  if( $hook != 'users.php' )
    return;

  wp_enqueue_script( 'tablesorter', plugins_url( 'js/jquery.tablesorter.js' , dirname(__FILE__) ), array( 'jquery' ) );
  wp_enqueue_script( 'custom-js', plugins_url( 'js/custom.js' , dirname(__FILE__) ), array( 'tablesorter' ) );
}
add_action('admin_enqueue_scripts', 'awordpress_load_scripts');

where in the custom.js you should put something like the following

jQuery(document).ready(function($) {
  $(".users").tablesorter();
});