sevenspark

The new accessibility javascript in the Appearance > Menus panel in WordPress 3.6 can significantly slow the page load speed when using a large number of menu items (> 50). This plugin defers the accessibility processing to eliminate the scripting bottleneck and allow the Appearance > Menus screen to run much faster and more responsively.
<a href="http://sevenspark.com/wordpress/speeding-up-the-appearance-menus-screen-in-wordpress-3-6" rel="nofollow ugc">Full details</a>
This solution is fairly rough. Hopefully we can develop a robust solution that can eventually become part of the core. Pull requests through GitHub are welcome.

Faster Appearance – Menus

Web Guy

VeryEasy

A set and forget solution for WordPress speed.
<a href="https://gtmetrix.com/" rel="nofollow ugc">Test your site speed</a> before and after.
Features
<ul>
<li>Add better cache handling</li>
<li>Add expires headers</li>
</ul>
Ask for help: <a href="mailto:help@veryeasy.io" rel="nofollow ugc">help@veryeasy.io</a>

Speed Made Easy

A set and forget solution for WordPress speed.

Faster Appearance – Menus vs Speed Made Easy