Someone from one of the forums I frequent, heard me lamenting that I only had 15 people signed up for my free newsletter in the past 6 months. He sent me an URL to check out. It's a site that works like an affiliate program, and it's free. You put a line of code in your website, which generates a pop-up everytime someone leaves your site. This pop-up is a sign-up for free newsletters, and the list refreshes to new offers each time. Every time your site displayes the pop-up, your newsletter offer receives 4 displays on other websites doing the same thing.
It did sound too good to be true, but since it was free, I signed up yesterday. Surprise, surprise, today I had two people sign up for my newsletter! Please don't misconstrue this as an ad, I'm genuinely pleased with this service. I'll include the link below, but if the moderator feels it's too much like advertising, I'll understand completely if he removes it.
Subscriver Drive