Brian Layman

This plugin allows the creation and display of custom sidebars for any page (or post) on your site. On each page, you can choose which of your current theme’s sidebars will be replaced. The replacement works for all descendants of a replaced page.
In this fashion you can: 
1. Easily create a CMS like site with unique sidebars for every page, even if your theme doesn’t support it. 
2. Create a sidebar with a Cart widget that displays on store pages created by the WP-E-Commerce page, but not anywhere else on the site. 
3. Use parent pages to create themed areas of your site, without creating custom page templates.
This plugin is compatible with every theme and all widgets because it hijacks your theme’s sidebars instead of replacing them.
<h3>Use</h3>
<ol>
<li>Edit a page or create and save one. It must at least have a title.</li>
<li>In the ?Custom Sidebar? section, check ?Activate a custom sidebar? and select the sidebar to replace.</li>
<li>On the Appearance->Widgets screen, place the widgets on the newly created sidebar that matches your post. </li>
</ol>
That?s it. No code. No CSS changes. No custom templates.
This video describes the usage of the plugin: 
 <iframe loading="lazy" class="youtube-player" width="640" height="360" src="https://www.youtube.com/embed/_U2XfrU7nZQ?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>

Per Page Sidebars

The Per Page Sidebars (PPS) plugin allows blog administrators to create a unique sidebar for each Page. No template editing is required.

ArielK

Yakir Sitbon

pojo.me

With Pojo Sidebars you can create as many sidebars you need for any page you want. Especially for themes based on <a href="http://pojo.me/?utm_source=wp-repo&utm_medium=link&utm_campaign=sidebars" rel="nofollow ugc">Pojo Framework</a>.
You can easily separate your site into sections, as well as set a specific sidebar for every single page or custom post type.
You can replace any sidebar with a different one by embedding it in the Text Editor with a unique shortcode.
Display a sidebar using a built-in shortcode:
<pre><code>[pojo-sidebar id="ID"]
</code></pre>
Display a sidebar using a WordPress function:
<pre><code><?php dynamic_sidebar( 'pojo-sidebar-ID' ); ?>
</code></pre>
Would you like to like to contribute to Pojo Sidebars? You are more than welcome to submit your requests on the <a href="https://github.com/pojome/pojo-sidebars/" rel="nofollow ugc">GitHub repo</a>. Also, if you have any notes about the code, please open a ticket on this issue tracker.

Pojo Sidebars

Pojo Sidebars generates as many sidebars as you need. It then allows you to place them on any Post, Page or Custom Posts Type in your WordPress site.

Per Page Sidebars vs Pojo Sidebars