Eric Marden

A custom plugin that will display dynamic text from the values you enter in special custom fields on a post inside of a WordPress Widget.
Add any text you want as the value of the ‘posty’ custom field and it will show up in this widget. Title the widget with the ‘posty-title’ custom field. It only works on single posts.
<h3>License</h3>
The Posty Widget plugin was developed by Eric Marden, and is provided with out warranty under the GPLv2 License. More info and other plugins at: http://xentek.net
Copyright 2008 Eric Marden (email : wp@xentek.net)
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Posty Widget

A custom plugin that will display dynamic text from the values you enter in special custom fields on a post inside of a WordPress Widget.

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.

Posty Widget vs Per Page Sidebars