link to a subsite in the navigation

[Carlos]

Another way to do it without plugins, if you only need to add links at the beginning or end of the menu, could be:
Find the get_navigation(...) tag in your template files. It should be between <ul>...</ul> tags. Insert a <li>...</li> with your external site link before or after the get_navigation call.

Example: in Innovation theme, header.inc.php file:

Code:

<!-- main navigation -->
                <nav id="main-nav">
                    <ul>
                        <li><a href="http://get-simple.info/">GetSimple CMS site</a></li>
                        <?php get_navigation(get_page_slug(FALSE)); ?>
                        <li><a href="http://google.com/">Google</a></li>
                    </ul>
                </nav>

(On most other themes it'd be in template.php)