Official WordPress URL with download, screenshots and more information: http://wordpress.org/extend/plugins/page-tree/
Do you have a WordPress site with lots of pages in a hierarchical structure? Are you trying to use WordPress like a “real” CMS? Then this plugin is for you!
Page Tree gives you a much-needed overview of your published pages in the admininstration panel using a common expand/collapse menu, which lets you navigate your page structure like a folder tree in Windows Explorer.
Now you can quickly and easily find the page you want to edit using the expandable tree view, and also get an admin view site map of your complete site.
The page tree is only displayed in WordPress administration panel, under your regular “Pages” menu. See the screen shot for a better understanding of how it works.