alfaguru

This plugin provides similar functionality to the <a href="http://drupal.org/project/sidecontent" rel="nofollow ugc">Drupal Side Content module</a>.
It enables you to define a set of widgets which are effectively placeholders. Each one is empty until you assign content 
to it when editing a page. 
This enables you to extend the content of the page into the sidebar.
Suppose, for example, you have a set of pages about people in your company. You could use a side content 
widget to add a biography for each of them, or a photo, or to list their favourite pizza toppings.
You can use the plugin without any template changes at all, but it does provide a simple API so you can test for the presence of side content widgets and adjust your templates accordingly.
As of release 0.7 of the plugin, it supports the <a href="https://codex.wordpress.org/Shortcode_API" rel="nofollow ugc">WP shortcode API</a>. There is also an extra add-on plugin which provides the same support for <a href="http://alexrabe.boelinger.com/wordpress-plugins/nextgen-gallery/" rel="nofollow ugc">NextGEN Gallery</a> shortcodes (development sponsored by <a href="http://www.comunicrea.com/" rel="nofollow ugc">Comunicrea s. n. c.</a>).
Release 0.75 fixes a bug affecting side content widgets with names containing characters other than lowercase alphanumerics. A new contributed extension provides integration with the qTranslate plugin.
Release 0.8 adds no new functionality but makes the plugin compatible with WP 2.7. 
Release 0.9 adds no new functionality but makes the plugin compatible with WP 2.8.1. 
Release 1.0 adds no new functionality but makes the plugin compatible with WP 4.1.0.
<h3>API</h3>
Use the following code to test for the presence of side content widgets:
<pre><code><?php if(function_exists('the_side_content') && the_side_content()->has_widgets() :?>
</code></pre>
Use the following code to test for the presence of a particular side content widget called ‘widget name’:
<pre><code><?php if(function_exists('the_side_content') && the_side_content()->has_widgets('widget name') :?>
</code></pre>
The plugin defines a filter, ‘side_content’, which can be used to preprocess side content widgets before display.

Side Content

Side Content enables you to create widgets which have different content on different pages.

Justin Tadlock

The Query Posts widget was written to allow users that don’t know their way around PHP to easily show posts in any way they’d like. It’s like having a cool WordPress developer as a friend ready to do your bidding. Seriously.
The widget has over 40 options to choose from. You can list posts by category, tag, custom taxonomies, author, date, time, name, or anything you can imagine. You can choose to show the full content, excerpts, or even a simple list. You can order the posts in all sorts of ways. Oh, and you can even show pages.
This is the widget that keeps users out of the code and gives them the ability to display items on their site how they want.

Query Posts

A WordPress widget that gives you unlimited control over showing posts and pages.

Side Content vs Query Posts