Add menu item to WordPress admin bar

admin_bar_menu
function custom_node_example($wp_admin_bar){
    $args = array(
        'id' => 'custom-node',
        'title' => 'Custom Node',
        'href' => 'http://example.com/page/',
        'meta' => array(
            'class' => 'custom-node-class'
        )
    );
    $wp_admin_bar->add_node($args);
}

add_action('admin_bar_menu', 'custom_node_example', 50);