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: 
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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.

Ben Byrne

kenjigarland

Xavier Serrano

Anything you can do with a widget can now be done inside your menus!
Widget Menuizer makes WordPress menus even more powerful, allowing for easy creation of custom “mega menus” and other fanciness without completely overhauling the menu management system into something unrecognizable.
Upon activation, navigate to the menu management screen under Appearance > Menus, and you’ll find a new option for Sidebars under the familiar Pages, Posts, Links, Categories and Tags list. Here, you can view all the sidebar regions that exist in your currently-active theme. Simply check a box to add a sidebar into your menu the same way you would for any other menu item.
Once in your menu, you’ll see a new option for “Container Element,” which specifies which HTML tag is wrapped around the sidebars that are output into the menu.
While running Widget Menuizer you also get the ability to define new sidebar regions right from the Appearance > Widgets admin screen (when using WordPress prior to 5.8, or 5.8 in conjection with the Classic Widgets plugin), so you can easily create new regions just for including in your menus without having to write any custom code for your theme.
Note for users of WordPress 5.8 and above: This plugin still works for injecting regions into menus, but you need to run the “Classic Widgets” plugin in order to create new Widget Areas via the admin.
Important: Because it’s possible to put menu widgets inside sidebars, you may see a warning notice if the sidebar region you’ve put in your menu contains a menu widget. This is because you may have inadvertently created a recursion: if the menu contained in your sidebar is the same menu your sidebar is placed in, you’ll have an infinite loop that will do bad, bad things. So be careful.
New in 1.0 Widget Menuizer now gives site administrators the ability to control the direction widgets flow within the menu, either horizontally or vertically.
New in 0.6: Widget Menuizer now provides a way for site administrators to create new Sidebars on the fly from the Widget admin! Now you can create new sidebars for use in your menus without having to edit your theme files or use some other plugin to let you register new sidebars.

Widget Menuizer

Unlock the full potential of the WordPress menu system to create mega menus and more by adding sidebar regions and widgets to your menus.

Per Page Sidebars vs Widget Menuizer