Ben Huson

<h4>Add missing classes</h4>
Adds missing classes for selected menu states. Classes added include:
<ul>
<li><code>current-page-parent</code> and <code>current_page_parent</code></li>
<li><code>current-page-ancestor</code> and <code>current_page_ancestor</code></li>
<li><code>current-menu-ancestor</code></li>
<li><code>current-menu-parent</code></li>
</ul>
The classes are added in the following scenarios:
<ul>
<li>When viewing an attachment page classes are added to any parent pages and their menu ancestors.</li>
<li>When viewing a post classes are added to any relevant taxonomy menu items and their manu ancestors.</li>
</ul>
<h4>Manage Menu Select States</h4>
Allows you to control which menu items should be selected (or deselected) when viewing certain pages of your site. You need to add classes to the menu items for this to work.
<ul>
<li><code>ecms-archive-{$post_type}</code> – Select menu item when viewing a post type archive page.</li>
<li><code>ecms-single-{$post_type}</code> – Select menu item when viewing a single post type page.</li>
<li><code>ecms-taxonomy-{$taxonomy}</code> – Select menu item when viewing a taxonomy archive.</li>
<li><code>ecms-taxonomy-{$taxonomy}-term-{$term}</code> – Select menu item when viewing a taxonomy term archive.</li>
<li>
<code>ecms-404</code> – Select menu item when viewing a 404 page.
</li>
<li>
<code>ecms-no-archive-{$post_type}</code> – Deselect menu item when viewing a post type archive page.
</li>
<li><code>ecms-no-single-{$post_type}</code> – Deselect menu item when viewing a single post type page.</li>
<li><code>ecms-no-taxonomy-{$taxonomy}</code> – Deselect menu item when viewing a taxonomy archive.</li>
<li><code>ecms-no-taxonomy-{$taxonomy}-term-{$term}</code> – Deselect menu item when viewing a taxonomy term archive.</li>
<li><code>ecms-no-404</code> – Deselect menu item when viewing a 404 page.</li>
</ul>

Extra Classes

Adds classes for selected menu states such as highlighting categories when viewing a blog post or parent page when viewing an attachment page.

duzymaju

This simple plugin was written to add classes to first, last, parent, even and odd elements of wp_page_menu and wp_nav_menu to support recognizing it in older browsers without :first-child, :last-child and :nth-child supporting.
Plugin adds the following classes to menu <li> tags:
<ul>
<li>“first-menu-item” to every first child of <ul> or <menu> tag,</li>
<li>“last-menu-item” to every last child of <ul> or <menu> tag,</li>
<li>“parent-menu-item” to every child of <ul> or <menu> tag that has another <ul> or <menu> tag inside (a parent to another menu level),</li>
<li>“odd-menu-item” to every odd child of <ul> or <menu> tag, including first and/or last child,</li>
<li>
“even-menu-item” to every even child of <ul> or <menu> tag, including first and/or last child.
Above classes are added separately to each menu level. Plugin use SimpleXML extension and requires PHP 5 or higher. Menu should have valid XHTML code.
</li>
</ul>

MAJpage Menu Class Extender

Adds classes to first, last, parent, even and odd elements of wp_page_menu and wp_nav_menu.

Extra Classes vs MAJpage Menu Class Extender