Remove / add from the WP admin bar I found this useful in a multisite install where I wanted network sites to link back to the main site homepage, as opposed to the individual network site homepage

functions.php

function ak_admin_bar_nav($wp_toolbar) {
	$wp_toolbar->remove_node('comments');
	$wp_toolbar->remove_node('new-content');
	$wp_toolbar->remove_node('my-sites');
	$wp_toolbar->remove_node('wp-logo');
	$wp_toolbar->add_node(array(
		'id' => 'theid',
		'title' => 'A Title',
		'href' => 'http://linkurl.com'
	));	
		
}
add_action('admin_bar_menu', 'ak_admin_bar_nav', 999);