I needed a widget for a site that only shows the subpages of a page while on the parent page. I found the Flexi Pages Widget. It is easy to implement and with a little tweeking I got exactly the result I wanted.
Here is a quote from the site:
Flexi Pages Widget is a highly configurable widget to list pages and sub-pages in WordPress sidebar. User friendly widget control comes with plenty of options. ‘Flexi Pages’ widget can be used as an alternative to the default WordPress ‘Pages’ widget.