James Irving-Swift

Electric Studio

Adds a filter in your wp-admin that allows you to choose a parent page so that only the children of that page will be shown. Very useful if you have a lot of pages! 
Thank you to Brian Krogsgard for the changes in version 1.3 (Twitter: @Krogsgard)

Filter Pages by parent in admin

Filter pages in the wp-admin by their parent pages

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.

Filter Pages by parent in admin vs Simple Page Hierarchy Widget