Marcus Downing

When writing or modifying a theme, the function wp_nav_menu() displays the contents of menus configured in your settings. If you have a lot of little menus the list can get hard to manage, so this plugin lets you group several menus under a single menu.
To use it, simply add a <code>submenu</code> parameter to the arguments of wp_nav_menu, like so:
<pre><code>wp_nav_menu(array(
 'menu' => 'header',
 'submenu' => 'About Us'
));
</code></pre>

Subtitle Filter

Adds tha ability to show only a submenu with wp_nav_menu().

Jon Christopher

Breadcrumbs are often generated from Page structure, but in a world of Custom Post Types that doesn’t always work. Menu Breadcrumb uses your WordPress Menu to generate a breadcrumb trail based on the current page.
<a href="https://github.com/jchristopher/menu-breadcrumb" rel="nofollow ugc">View on GitHub!</a>

Menu Breadcrumb

Generate a breadcrumb trail from a WordPress Menu

Subtitle Filter vs Menu Breadcrumb