Peter Westwood

This plugin allows you to run loops within your WordPress templates where you query for children of the current page.
The plugin extra arguments to the list of arguments supported by query_posts().
The query argument <code>child_of</code> is used to add a WHERE to the database query to limit the pages returned to those with a post_page equal to the argument provided.
The query argument <code>child_limit</code> is used to limit the number of pages returned.
The query argument <code>child_offset</code> is used to offset the limiting to allow for pagination if required.

PJW Query Child Of

This plugin allows you to run loops within your WordPress templates where you query for children of the current page.

BeardedGinger

Designed to display the Parent, Child, and Grandchild hierarchy in the most straightforward way out of the box.
This plugin will provide a widget that locks the Parent page as the widget title.
If this is a child of the top parent, the widget will display the Parent as the title of the widget and a ul of links for all siblings of the current page.
If this is a grandchild of the top parent, the Widget will display the same as the scenario above with the addition of a sub ul of all siblings of this grandchild.
Test it out, if it doesn’t work like you want out of the box, this plugin isn’t for you.

Simple Page Hierarchy Widget

Displays the most logical arrangement of Parent, Child, & Grandchild pages.

PJW Query Child Of vs Simple Page Hierarchy Widget