As you may know, the websites Facebook.com and Twitter.com are on its boom. So why not capitalize on this and make the most of these social networks?
Create a fan page for your business on Facebook and Twitter, invite your contacts to join and ask them to invite their contacts. This will also help to promote their newsletters, because that way, they can put the links of these bulletins, and on these pages. You can also ask the new fans who are interested in receiving information in their emails to register to your subscription form; this will make your list grow even more.
Actually, you can take advantage of these social networks not only to gain new customers but also to promote their e-marketing newsletters.