Ninja Kick: Subscription WordPress Plugin is a premium list building plugin that adds subscription form with push/sliding animation effect and clean design on every page of your site. It's simple-to-use yet powerful tool with a lot of opening patterns and analytics available. With this product you can easily increase the number of your subscribers rocketing your traffic this way!
Demo: http://codecanyon.net/item/ninja-kick-subscription-wordpress-plugin/8969399/