Delink Pages 1.1 by Jennifer Stuart is now available.
There were some issues with first release of the plugin. Jennifer addressed them all in this new release... and more.
Recently I found Delink Pages 1.0 plugin by Jennifer Stuart. It promises something I was looking for:
This plugin will allow you to specify certain pages to not be linked when wp_list_pages() is used in a theme. You might want to do this if you want a header for a series of subpages, but don't specifically want that header to be a real page itself.