/**
 * Implements hook_node_load().
 */
function {{ machine_name }}_node_load($nodes, $types) {
  // Decide whether any of $types are relevant to our purposes.
  if (count(array_intersect($types_we_want_to_process, $types))) {
    // Gather our extra data for each of these nodes.
    $result = db_query('SELECT nid, foo FROM {mytable} WHERE nid IN(:nids)', array(':nids' => array_keys($nodes)));
    // Add our extra data to the node objects.
    foreach ($result as $record) {
      $nodes[$record->nid]->foo = $record->foo;
    }
  }
}