KingSumo remains our perennial favorite for viral giveaways.
This web app lets you grow your email list using viral social giveaways across multiple websites. The original version was a WordPress plugin.
It helps you create viral giveaways so you can grow your audience and get more leads quickly and effectively. Its easy-to-use editor will have your first giveaway set up and running in minutes. All you need to do is write a little bit about your giveaway and pick the number of winners you want.