Andreas Norman

This plugin simply lists all subpages from a selected parent page (with option do exclude specific pages) in the sidebar. This widget can be placed many times in your sidebar.

SubZane Sub Page List Widget

Lists all subpages from a selected parent page with option do exclude specific pages.

Nile Flores

WP Subpages Widget is a simple plugin to allow for multiple instances to show child pages. For people who use multiple template files for each of their site’s pages, having the capability of using a widget, rather than hardcode subpages of a parent or child page.
While the WordPress 3.0 Menu System allows users to be able to create a menu system with child pages, this plugin works with the natural Page hierarchy. It’s great for sections of the website that have sub pages like alphabetical pages, and more.

WP Subpages

WP Subpages Widget is a simple plugin to allow for multiple instances to show child pages.

SubZane Sub Page List Widget vs WP Subpages