jonaspiela

Add a short teaser text with page thumbnail and link it to a page in your sidebar. The plugin takes care of correct linking. I am using the plugin on my own <a href="http://www.jonaspiela.com/" title="Jonas Piela" rel="nofollow ugc">website</a>.
Check out more details and screenshots <a href="http://www.jonaspiela.com/2010/12/24/wordpress-plugin-page-teaser-widget/" rel="nofollow ugc">here</a>.

Page Teaser Widget

Easily promote pages in you sidebar and forget about not updated links.

RaveKev

This plugin provides a widget that can be embedded into pages to show a list of subpages of a selected page.
For example you can use this widget to display a list of your products. Just insert the widget on any page and select the parent page for your products as “parent page”.
You can choose if you
<ul>
<li>want to display page images or not</li>
<li>want to show the whole text or just the excerpt</li>
<li>want to switch the side of your texts and images for each product</li>
<li>want to hide some pages</li>
<li>want to hide empty pages</li>
<li>want to show just a few pages</li>
<li>want to show the pages in a certain order or just display it randomly</li>
<li>want to show subpages from another page</li>
<li>etc.</li>
</ul>

A Sub Site Teaser Widget

Teasers subpages as list with images and text / excerpt

Page Teaser Widget vs A Sub Site Teaser Widget