This plugin is very simple and straightforward. Just enter ?{list}? on each parent page or post where you want the children listed. Put it anywhere in your content and that is where it will show.
Then in your css..
.subpage-style { Put your styles here };
Easy as pie!

Andy's List Subpages Plugin

Nice and simple plugin that lists the children of a certain page or post in…

WenZe

Category Parent Children Selector is a WordPress plugin that helps you in selecting parent-children categories.
Features include:
<ul>
<li>Button to select all categories. </li>
<li>Button to select all categories including children categories. </li>
<li>Button to select first level of children categories only. </li>
<li>Button to select parent and all its children categories under its sub categetory. </li>
<li>Auto select parent categories when a sub category is selected.</li>
</ul>

Category Parent Children Selector

Helps you in selecting parent-children categories.

Andy's List Subpages Plugin vs Category Parent Children Selector