thunderbax

The plugin add a custom page in your admin dashboard where you can show html code to editors. 
You can edit the html text directly in a box place in option page with a WYSIWYG editor. 
All html, javascript, css are supported. 
You can also insert Youtube videos or images.
Related Links:
<ul>
<li><a href="http://www.thunderbax.com/?page_id=767" title="WP Admin Custom Page Plugin for WordPress" rel="nofollow ugc">Plugin Homepage</a></li>
<li><a href="http://www.thunderbax.com" title="Author Homepage" rel="nofollow ugc">Author Homepage</a></li>
</ul>

WP Admin Custom Page

The plugin add a custom page in your admin dashboard where you can show html code to editors.

Justin Tadlock

Hybrid Hook is a plugin that allows end users the ability to tap into the <a href="https://wordpress.org/extend/themes/hybrid" title="Hybrid WordPress theme framework" rel="ugc">Hybrid theme’s</a> extensive hook selection by providing a user interface in the WordPress admin for adding custom content.
You must be using at least version 0.9 of the <a href="https://wordpress.org/extend/themes/hybrid" title="Hybrid theme" rel="ugc">Hybrid theme</a> for this plugin to work. It will also not work with any other themes.
Features:
<ul>
<li>Ability to add custom HTML nearly anywhere on your site.</li>
<li>Use shortcodes to quickly add content.</li>
<li>Allows the input of JavaScript.</li>
<li>User can select the priority the code will run.</li>
<li>Can execute PHP code if the option is selected.</li>
</ul>

Hybrid Hook

Allows the addition of HTML, shortcodes, PHP, and/or JavaScript to the Hybrid theme's hooks from the WordPress admin.

WP Admin Custom Page vs Hybrid Hook