This is a recursive function that allows the user to display an unlimited number of levels and children in a static menu. It also allows you to limit the number of children that are displayed for particular pages. This is achieved with an array of slug/limit pairs. The function's options are:

1. required, The page from where you want to start displaying the menu;
2. required, The current page;
3. optional, If true, start with a <UL>
4. optional, An array of slug/limit pairs where limit is the maximum number of children to display for that particular slug.

<?php
function displayChildren($page, $current, $startmenu = true, $limits = null) {
  if ($limits != null && array_key_exists($page->slug, $limits)) {
    $arr = array('order' => 'position ASC, published_on DESC', 'limit' => $limits[$page->slug]);
  } else
    $arr = array('order' => 'position ASC, published_on DESC');
  if ($page && count($page->children()) > 0) {
    echo ($startmenu) ? '<ul>' : '';
    foreach($page->children($arr) as $menu) :
        echo '<li'.(in_array($menu->slug, explode('/', $current->url)) ? ' class="current"': null).'>'.$menu->link($menu->title);
        displayChildren($menu, $current, true, $limits);
        echo '</li>';
    endforeach;
    echo ($startmenu) ? '</ul>' : '';
  }
}
?>

Just add the above function to a Snippet or Layout. Then you can use the following code on a page somewhere to produce the actual menu:

<h1>Menu</h1>
<?php
  $page = $this->find('/');
  echo '<ul class="sidemenu">';
  echo '<li>'.$page->link($page->title, (in_array($page->slug, explode('/', $this->url)) ? ' class="current"': null)).'</li>';
  echo displayChildren($page, $this, false, array('articles' => '3', 'a-sub-page' => '1'));
  echo '</ul>';
?>