BACK TO DIRECTORY
With this plugin you can add extra HTML or just plain text when posting a new page or post. That content will be displayed in sidebar widget. It is tested from WP 2.6 to 3.0.1.
Screenshots
Posting area with ax-sidebar section opened (WP 2.6)
Sidebar showing that contents inserted in posting area for this post(WP 2.6)
Added widget in theme menu at admin side (WP 2.7.1)