From: Daniel Watrous,

The optincrusher is a tool that was developed to increase the optin rate on your website. It does this by getting the user’s attention, without interrupting him. The result is virtually no increase in bounce rate by a significant increase in your optin rate. It’s the easiest and fastest way to build an email list in wordpress.

You can download the optincrusher for free from my website (danielwatrous.com) at the following link: