Shortcode for showing childpages

Put this in your theme’s functions.php, it will add the shortcode [child_pages]:

function wpsc_child_pages($atts){
    global $wp_query;
    $html="";
    if( empty($wp_query->post->post_parent) ) {
        $parent = $wp_query->post->ID;
    } else {
        $parent = $wp_query->post->post_parent;
    }
    $pages = wp_list_pages("title_li=&child_of=$parent&echo=0");
    if( $pages ){
        $html .= "<div><ul>$pages</ul></div>";
    }
    return $html;        
}

add_shortcode('child_pages', 'wpsc_child_pages');

If you want to pass the function variables (e.g. [child_pages parent=3]) you would access that variable using the passed $atts argument.