Currently, it is possible to display links to your pages in the sidebar using the Page widget. However, there aren't any options, and when the the widget is enabled, all pages are listed. If many sub-pages have been created, this makes for a very long list -- rather unfriendly.
It would be very helpful if we had the the option of listing all pages or only parent pages on the Page widget. That, or allow users to customise their page sidebars! (I'd love to see this.) This way, we could place an extra box on pages that display the sub-pages.
Eg. on the "Simpson" page, an extra box on the side with links to "Homer", "Marge", "Lisa", etc; and then on the "Lisa" page, an extra box with links to "Bio", "Quotes", "Interview", etc.
Of course, links to the sub-pages could simply be listed on the parent page, but putting them in the sidebar would make navigation much easier as visitors won't have to go back and forth between the parent page and the sub-page. Possibly making it act a bit like a framed page, but, well... :)