Show Widget Area Names (SWAN)
by Amplitude Design on WordPress.org
Plugin to show the widget area names on non-admin pages and posts. This adds the title to widget $params['before_widget'].

How the widget name is outputted on the page.
If you get confused by which widget area a widget is attached to when browsing your site then this plugin can help.
The plugin shows the widget area names on non-admin pages and posts. This adds the widget area title to widget $params[‘before_widget’]. This will only display for the edit_posts capabilities. You must use print $params[‘before_widget’] in your widget definitions to view the area name.
If the widget area is empty then no widget area name is displayed.
Recently added a jQuery toggle to the admin menu bar to quickly hide/show the widget area names. See +/- swan link in admin bar.