Internet123

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.
<h3>Compatibility</h3>
The plugin has not been tested below version 3.3.

Per Page Widgets

Control widget areas on a per-page / per-post basis.

Ederson Peka

With this plugin, you can create as much “sidebars” (widget areas) as you need, and assign them in a per-page basis. (It’s only useful if your theme supports “sidebars”.)
WARNING: Updating from versions prior to 0.2.5 requires new set up.

Unlimited Page Sidebars

This plugin does exactly what it needs to and always works. It's great.

Does exactly what it needs to!

Assign one specific widget area (sidebar) to each page.

Per Page Widgets vs Unlimited Page Sidebars