Add nodes to a Drupal nodequeue programatically

add_nodes_to_nodequeue.php

<?php

  // List of nids of the nodes to add
  $nids = array(6474, 6475);

  // Get queue and subqueue information
  $queue_machine_name =  'queuename';
  $queue = nodequeue_load_queue_by_name( $queue_machine_name );

  // Get subqueues
  $subqueues = nodequeue_load_subqueues_by_queue( $queue->qid );

  // If we have only one queue just use the first (and only one)
  $subqueue = array_pop( $subqueues );

  // Add each node to the Queue
  foreach($nids as $nid) {
    nodequeue_subqueue_add( $queue, $subqueue, $nid );
  }