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Manage and write aside posts (using the new custom post types feature). 
They are displayed in a sidebar widget and don’t interfere with other posts. 
A dashboard widget is provided to allow fast aside blogging.
Require WordPress 3 and PHP 5.
Aside content must be write in post title. 
If you write something in post content (like a video embed), a link to this content will be displayed after the aside.
Asides can be automatically posted on Twitter and/or Facebook and/or Identica (Status.Net). 
A Twitter app is preconfigured. 
For Facebook, you need to create your own application. Video tutorial included in contextual help on settings page.
When asides with additional content are published to Twitter a shortlink to the full content is added.
Supported shortlink providers :
<ul>
<li>Native (blogurl?p=post_ID)</li>
<li>is.gd</li>
<li>bit.ly (api key needed)</li>
<li>jm.p (api key needed)</li>
<li>goo.gl</li>
<li>tinyurl.com</li>
<li>su.pr</li>
<li>cli.gs</li>
<li>twurl.nl</li>
<li>fon.gs</li>
</ul>

Sideblogging

Display asides in a widget. They can automatically be published to Twitter, Facebook, and any Status.net installation (like identi.ca).

A plugin that enables you to have dedicated content and/or widget sidebar for each specific page or post. For example, on a featured blog post you may want to place additional contact while on a calendar page you might want to place a calender widget or some text events or both.
<h3>Widget Support</h3>
Widget support is enabled by default and you do not have to add any code. The only recommended change is that you go to your template’s functions.php file and remove any coding containing a function similar to the one below.
<pre><code>if ( function_exists('register_sidebar') )
 register_sidebar();
</code></pre>
To enable widgets on a page or post, go to the manage screen and click ‘Add Widgets!’ to add or ‘Remove Widgets’ to remove.
<h3>Notes</h3>
This plugin is ONLY for WordPress 2.5+. It will not work with lower versions and may in fact corrupt the data in older versions. Please stay up to date with both WordPress and this plugin.
When using this plugin instead of Page Sidebars, this plugin will overwrite any of the widget configurations previously used. Also, do NOT use this script with Page Sidebars as it will lead to compatibility issues. Using this plugin will overwrite your other widget sidebars defined in your template. Proceed with caution.
For an older version of this plugin for WordPress versions 2.3.3 or lower, check out Page Sidebars.

Core Sidebars

A small but useful plugin to have unique sidebars for each page/post.

Sideblogging vs Core Sidebars