Jon Schroeder

This plugin should only be used on Genesis sites (on non-Genesis sites, it won’t break anything, but it also won’t do anything at all).
Once the plugin is active, you’ll be able to see it in action by going to any parent page or child page which shows the Primary widget area. Navigating to either the parent page or a subpage will keep the same menu in place (it shows the top-level page and the child pages of that top-level page).
Custom post types are fully supported, as long as they are heirarchical.
This plugin replaces the primary widget area with this subnavigation. When you scroll down on a long page on which that new subnavigation appears, the subnav will scroll with you.

Genesis Subpage Sidebar

This plugin replaces your Genesis primary sidebar with a list of child pages (supports custom post types). Only works with Genesis child themes.

mitcho (Michael Yoshitaka Erlewine)

This plugin makes it easy for you to add a new subpage to a page you are currently viewing. The plugin adds the following:
<ol>
<li>a widget which, when enabled, displays a “add subpage” link in your widget areas of pages;</li>
<li>a “Subpage” item to the “Add New” menu on the admin menu bar.</li>
</ol>
This plugin is a component of the <a href="http://ecs.mit.edu" rel="nofollow ugc">MIT Educational Collaboration Space</a> project.

Add Subpage Here

Adds simple widget and admin menu item for adding a subpage to the current page.

Genesis Subpage Sidebar vs Add Subpage Here