Sibin Grasic

Responsive Videos plugin will allow you to automatically resize and scale your embedded videos on mobile devices. 
CSS selector option is provided so you can target only your post / page content container.
Features
<ul>
<li>Automatic configuration option</li>
<li>Automatically resizes / scales all your embedded videos</li>
<li>Works on all browsers</li>
<li>Highly compatible – you can change the css selector for the text highlight</li>
<li>Customizable – you can select the page type on which to activate the fitVids script</li>
</ul>

Responsive videos – Fitvids

Nice one

Good

Make your Embedded videos responsive on mobile devices with jQuery FitVids plugin

Kevin Dees

This plugin makes videos responsive using the FitVids jQuery plugin on WordPress.
The options page is located on the dashboard menu under Appearance as “FitVids”. FitVids always works with YouTube, Vimeo, Blip.tv, Viddler, and Kickstarter. Use simple jQuery selectors, on the admin page, like <code>body</code>, <code>article, aside</code> and <code>.post</code> to customize what videos become responsive.
You can set custom selectors to include videos from any provider. You are not limited to the list that comes with FitVids by default.

FitVids for WordPress

Works great

Never been easier to have fitvids work like this. 5-star for sure!

Install, activate it, and everything just works

This plugin makes videos responsive using the FitVids jQuery plugin on WordPress.

Responsive videos – Fitvids vs FitVids for WordPress