How to add Custom Post Admin Icons to Wordpress

As of wordpress 3.8 it's really simple to add Custom Icons to Wordpress Admin. Use Dashicons! Dashicons is the official icon font of the WordPress admin as of 3.8. In your custom post type initialization add the "menu_icon" option.

$args = array( 'menu_icon' => 'dashicons-video-alt3', );

There's a great selection of icons you can use.