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.

softwud

The Page Blocks plugin extends your WordPress pages by combining the dynamic content of widgets with the static content of pages. Up to four “blocks” can be added to each page (two above and two below the page’s content), and widgets can be added to each block in the same way they are added to sidebars.
Content can be edited simply through the admin backend, removing the need for custom page templates for all but the most complex of blog designs. Two examples of what can be done with the plugin are shown in the Screenshots section:
<ul>
<li>
A home page with a welcome message in the page content above a widget displaying News posts on the left and a widget displaying the most recently created post on the right.
</li>
<li>
A page showing a dynamically generated “Thank You” message for a customer returning from PayPal in a single page block at the top of the page using a standard text widget and the Exec-PHP plugin (before and after images).
</li>
</ul>
More detailed information is available on the <a href="http://wordpress.softwud.com" title="Page Blocks Plugin Website" rel="nofollow ugc">Page Blocks Plugin Website</a>, as well as support and contact information. You can also contact SoftWUD through this site if you’d like a custom theme, plugin, or widget developed.
<h4>Features</h4>
<ul>
<li>
No file editing needed
Blocks are configured through the Page Write / Manage and Widgets admin pages. There is no need to edit PHP code or modify your theme in any way.
</li>
<li>
Blocks will work even if the theme is changed
As long as the theme you use employs the WordPress “Loop” mechanism (and pretty much all themes do) then there won’t be any problems. Even if the “Loop” has been modified.
</li>
<li>
Each page can be configured with a different set of page blocks
There are four blocks that can be enabled for each page – Top Left, Top Right, Bottom Left, and Bottom Right. For example you may have a Top Left on one page, a Bottom Left and Bottom Right on another, and all others may have none at all.
</li>
<li>
Each block can have it’s own CSS styling rules
The plugin provides default CSS styling for the blocks assuming that all four blocks are enabled on a page. However CSS styling rules can be applied through the Page Write / Manage admin page to override these, or even your own theme’s styling rules.
</li>
<li>
The plugin supports password protected pages
If you protect your page content with a password, the page blocks will also be hidden until the user enters a valid password.
</li>
</ul>

Page Blocks

This plugin extends WordPress pages by allowing widgets to be placed above and below the page content reducing the need to code custom page templates.

Per Page Sidebars vs Page Blocks