Adding custom links to header.php

Hi, I want to add a couple of outgoing links (i.e. to other websites) in my header.php file, alongside the links to the pages on my website:

<?php wp_list_pages('title_li='); ?>

So in other words I’d like to somehow add custom hyperlinks into the header, so it appears like: CustomLink1 | About | Contact etc

How do I do this? Thanks in advance!!