How to Attach a navigation menu to the admin bar (from: http://wpsnipp.com/index.php/functions-php/attach-a-navigation-menu-to-the-admin-bar/)

attach_nav_menu_to_admin_bar.php

<?php
add_action( 'admin_bar_menu', 'wpse15186_admin_bar_menu' );
function wpse15186_admin_bar_menu( &$wp_admin_bar )
{
    $menu = wp_get_nav_menu_object( 'WPSE 15186 test menu' );
    $menu_items = wp_get_nav_menu_items( $menu->term_id );

    $wp_admin_bar->add_menu( array(
        'id' => 'wpse15186-menu-0',
        'title' => 'WPSE 15186 menu',
    ) );

    foreach ( $menu_items as $menu_item ) {
        $wp_admin_bar->add_menu( array(
            'id' => 'wpse15186-menu-' . $menu_item->ID,
            'parent' => 'wpse15186-menu-' . $menu_item->menu_item_parent,
            'title' => $menu_item->title,
            'href' => $menu_item->url,
            'meta' => array(
                'title' => $menu_item->attr_title,
                'target' => $menu_item->target,
                'class' => implode( ' ', $menu_item->classes ),
            ),
        ) );
    }
}