by Jacob N. Breetvelt on WordPress.org
This plugin is a replacement for the standard Page widget, that works how you want it to do.

The display of the standard WP Pages widget
This plugin works like the standard Page widget, however this one works how you want it to do.
This plugin displays initially the pages menu top-level pages only.
While on a page, the child pages that belong to the page are also listed.
While on a child-page, the subsequent grand-child pages are listed also.
Etc. as deeply as reuired.
Additionally a Home-link can be added that will display conditionally.
You can select from: Always, On a page only, Never.
When On a page only is selected, the Home link will display ony when you are on a page, so when you might need it.
The advantage of this plugin is that a huge amount of pages can be in a menu, without the user getting lost as long as you provide a proper tree-structure to them.
The standard configurability of Widget title, Excluded pages, Sort order.
WP Photo Album is released under the GNU GPL licence. ( http://www.gnu.org/copyleft/gpl.html )