by Internet123 on WordPress.org

The default box added to the edit page for each page or post. By default the setting is "Standard" which means the Per Page Widgets will not affect your current sidebar and widget setup. The plugin also adds a little link to edit widget directly in an overlay.
Control widget areas on a per-page / per-post basis.
Gives you the ability to show or hide individual widget areas on each page / post as well as completely substituting the widgets shown in a specific widget area on a specific page or post.
The plugin has not been tested below version 3.3.