WhizKins

WPSimpleInsert is a plugin to insert custom code in your blog posts. It includes options to either add the code above 
or below post content.
Features:
<ul>
<li>Add custom HTML/PHP/JavaScript to your posts.</li>
<li>Ability to add custom code above or below post content.</li>
<li>Options to hide the code from certain pages like the home page and category and archives pages.</li>
</ul>

WP Simple Insert

A plugin to insert custom HTML or PHP code in your posts. Includes options to insert before or after post content.

WP Simple Insert vs Embeds for YouTube