How can I add a caption to my navigation menu?
function MYTHEME_menu_item_link($link) { 
  // Debug:
  // dpm($link);

  // Check menu item localization settings:
  if (empty($link['localized_options'])) {
    $link['localized_options'] = array();
  }

  // Target the desired menu:
  if ($link['menu_name'] == 'primary-links' &amp;&amp; $link['options']['attributes']['title']) {

    // Theme menu item description:
    $desc = '&lt;span class="menu-item-desc"&gt;' .
      check_plain($link['options']['attributes']['title']) .
    '&lt;/span&gt;';

    // And title:
    $link['title'] = '&lt;span class="menu-item-title"&gt;' .
      check_plain($link['title']) .
    '&lt;/span&gt;';

    // HTML should be enabled:
    $link['localized_options']['html'] = TRUE;

    // Theme the menu item title as a link, then append the description:
    return l($link['title'], $link['href'], $link['localized_options']) . $desc;
  }
  // For other menus:
  else {
    return l($link['title'], $link['href'], $link['localized_options']);
  }
}



Place this into your theme's template.php
Don't forget to flush your Drupal cache at admin/settings/performace (D6)