Heine

function example_elements_form() {
  $form = array();

  $header = array(
    'title' => array('field' => 'n.title', 'data' => t('Title')),
    'author' => array('field' => 'u.name', 'data' => t('Author')),
  );

  $query = "SELECT n.nid, n.title, u.name FROM {node} n INNER JOIN {users} u ON n.uid = u.uid". tablesort_sql($header);

  $result = pager_query(db_rewrite_sql($query));

  while($partial_node = db_fetch_object($result)) {
    $options[$partial_node->nid] = array(
      'title' => check_plain($partial_node->title),
      'author' => theme('username', $partial_node),
    );
  }

  if (!empty($options)) {
    $form['nodes'] = array(
      '#type' => 'tableselect',
      '#header' => $header,
      '#options' => $options,
    );

    $form['pager'] = array('#value' => theme('pager'));

    $form['submit'] = array(
      '#type' => 'submit',
      '#value' => t('Submit'),
    );

  }

  return $form;
}