hackadelic

When you use a shortcode in a text widget to dynamically create its content, the shortcode may yield empty content in some contexts, leaving you with an ugly looking empty widget in your sidebar with nothing more than a title and a blank rectange.
What you want is a text widget that will only show up when it does have content. This is such a widget.
A use case when you will immediately benefit from <a href="http://hackadelic.com/solutions/wordpress/discreet-text-widget" title="Discreet Text Widget" rel="nofollow ugc">Discreet Text Widget</a> is when you want a <a href="http://hackadelic.com/solutions/wordpress/toc-boxes" title="Hackadelic SEO Table Of Contents" rel="nofollow ugc">Table of Contents</a> <a href="http://hackadelic.com/table-of-contents-in-the-sidebar" title="How To Add a Table Of Contents to the Sidebar" rel="nofollow ugc">in the sidebar</a>.
Check out the <a href="http://hackadelic.com/solutions/wordpress/discreet-text-widget" title="Discreet Text Widget" rel="nofollow ugc">plug-in homepage</a> for in-depth information about the plug-in.
<h3>License</h3>
This file is part of the Hackadelic Discreet Text Widget WordPress plugin.
Hackadelic Discreet Text Widget is free software: you can redistribute it and/or modify it under the terms of the <a href="http://www.fsf.org/licensing/licenses/agpl-3.0.html" rel="nofollow ugc">GNU Affero General Public License</a> as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
Hackadelic Discreet Text Widget 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License along with Hackadelic Discreet Text Widget. If not, see <a href="http://www.gnu.org/licenses/" rel="nofollow ugc">http://www.gnu.org/licenses/</a>.

Hackadelic Discreet Text Widget

A smarter text widget that can be used to display table of contents in the sidebar.

Max Chirkov

Advanced Text Widget is a text widget that allows you to execute raw PHP code and specify on which pages it should be displayed. It comes with 10 default visibility conditions. You can edit and/or add your own visibility conditions as well. Conditions support arguments which could be strings and/or arrays.
Features:
<ul>
<li>10 Default widget visibility conditions with over 20 application possibilities.</li>
<li>Add unlimited custom conditions.</li>
<li>“Advanced Text” widget with raw PHP support and shortcodes execution.</li>
</ul>
PRO Version:
<ul>
<li>Apply visibility conditions to ANY widget.</li>
<li>Add custom CSS IDs/Classes to ANY widget.</li>
<li>Import/Export your visibility conditions to re-use on other sites.</li>
</ul>
<a href="http://simplerealtytheme.com/plugins/atw-pro/" title="Advanced Text Widget PRO" rel="nofollow ugc">Check out PRO Version</a>
Credits:
<ul>
<li>Author: Max Chirkov</li>
<li>Author URI: <a href="http://SimpleRealtyTheme.com" title="Real Estate Themes for WordPress" rel="nofollow ugc">http://simplerealtytheme.com</a></li>
<li>Copyright: Released under GNU GENERAL PUBLIC LICENSE</li>
</ul>

Advanced Text Widget

2nd EDIT: The plugin has now been updated, so my original review stands.

1st EDIT: Even though this was a great plugin in its day, it hasn't been updated in over 2 years and was flagged as vulnerable to attack when I ran WPScan. I therefore can't recommend it for now.

Original review: Can't imagine building a WordPress site without this, it's normally the first plugin one I install. Makes adding custom content to sidebars on a per-page basis an absolute breeze. Very flexible, you can type PHP and shortcodes in the text area and it displays whatever you want. A must have for any WordPress site developer.

Essential plugin for all my sites

Text widget with raw PHP support and conditional visibility settings. Flexible conditional options with ability to edit and add custom conditions.

Hackadelic Discreet Text Widget vs Advanced Text Widget