benknight

This is a simple plugin that was born out of working on several projects with sectional navigations. For example, consider the following common navigation tree structure:
<ul>
<li>Home</li>
<li>Item</li>
<li>About Us
<ul>
<li>Sub-item #1</li>
<li>Sub-item #2</li>
</ul>
</li>
<li>Item</li>
<li>Item</li>
</ul>
Then, whenever on the “About Us” page or any of its sub-items, it would output that peice of the navigation:
<ul>
<li>About Us
<ul>
<li>Sub-item #1</li>
<li>Sub-item #2</li>
</ul>
</li>
</ul>
This is particularly useful for websites that have a top horizontal navigation which shows top-level items and want to show a vertical subnavigation in the sidebar.
This plugin works by parsing the output of the <code>wp_nav_menu</code> function as XML and analyzing the CSS class hooks (current-menu-ancestor, current-menu-item, and current-menu-parent). Because it uses PHP’s SimpleXML library it therefore requires PHP 5+. It uses the theme’s registered menu locations.
This plugin also exposes the <code>section_subnav()</code> function for theme developers to use as a template tag to manually place a subnav inside the theme. Here is the usage:
<pre><code><?php

 section_subnav( array( // defaults
 'before_widget' => '<nav id="section-subnav" class="widget widget_section-subnav">',
 'after_widget' => "</nav>",
 'before_title' => '<h3 class="section-subnav-title widget-title">',
 'after_title' => '</h3>',
 'echo' => true
 ));

?>
</code></pre>
It returns false when there is no subnavigation.
This function also provides the <code>section_subnav_args</code> filter hook for writing less code and easier integration with other plugins and child themes.

Section Subnav

Adds a widget and template function for displaying subnavigation based on the current navigation state.

littlejon

LJ Subpages Widget allows you to display a menu listing subpages from a chosen page.
This plugin was developed as I needed a widget to display a list of subpages in my sidebar. All the other plugins that I found would only display subpages from the current page being displayed.
Features:
<ul>
<li>Will display the subpages of a chosen Parent page (as of version 1.1 will show subpages of current page if required).</li>
<li>Customizable Title with the choice of using the Parent Page Title or writing your own</li>
<li>Compatible with subpages of subpages. You have the option of displaying Subpages of the Subpages being displayed (This is theme dependant, your theme must support submenus in the sidebar for this option to function as expected)</li>
<li>If there are no subpages to display the widget outputs nothing rather then leaving a heading without any content</li>
</ul>
This widget was built using the new WordPress Widget API and as such it supports multi instance copies. For this reason it means that this widget is only supported by WordPress 2.8 and above. If you have a requirement for this plugin for a version of WordPress lower then 2.8 please contact me on the plugins homepage via a comment.

LJ Subpages Widget

LJ Subpages Widget allows you to display a menu listing subpages from a chosen page.

Section Subnav vs LJ Subpages Widget