There are a ton of ways to get people to sign up for your email marketing offers. I've put together a list for you to read, so you know all of the ways you can be growing your list.

1. Put an offer on the back of your business cards to get people to sign up for your newsletter.
2. Tradeshows - Bring a clipboard or sign-up book with you to tradeshows and ask for permission to send email to those who sign up.
3. Include a newsletter sign-up link in your signature of all of your emails.
4. Send an opt-in email to your address book asking them to join your list.
5. Join your local chamber of commerce, email the member list (if it's opt-in) about your services with a link to sign up to your newsletter.
6. Host your own event - Art galleries, software companies (one here has a party every quarter and invites the neighboring businesses), retail shops, consultants (lunch & learn) can all host an event and request attendees to sign up.
7. Offer a birthday club where you give something special to people who sign up.
8. Incentivize your employees - Give them $ for collecting VALID email addresses.
9. Giving something for free like a PDF? Make visitors sign up to your opt-in form before you let them download it.
10. Referrals - Ask you customers to refer you, and in exchange you'll give them a discount.
11. Bouncebacks – Get them back! - Send a postcard or call them asking for their updated email address.
12. Trade newsletter space with a neighboring business, include a link for their opt-in form and ask them to include yours in their newsletter.
13. SEO - Make sure you optimize your site for your keywords. You need to be at the top of the natural search when people are looking for your products or services.
14. Giveaways - Send people something physical and ask for their email address as well as their postal address.
15. Do you have a postal list without emails? Send them a direct mail offer they can only get if they sign up to your email list.
16. Include opt-in forms on every page on your site.
17. Popup windows - When someone attempts to leave your site, pop up a window and ask for the email address.
18. Include a forward-to-a-friend link in your emails just in case your recipient wants to forward your content to someone they think will find it interesting.
19. Include a forward-to-a-friend on every page of your site.
20. Offer a community - Use Ning as your easy-to-set-up community and have your visitors interact and sign up for your newsletter.
21. Offer "Email only" discounts and don't use those offers anywhere but email.
22. Telemarketing - If you've got people on the phone, don't hang up until you ask if you can add them to your newsletter.
23. Put a fishbowl on your counter and do a weekly prize giveaway of your product - then announce it to your newsletter. Add everyone who put their card in on to your newsletter list.
24. Include an opt-in form inside your emails for those people who get your email forwarded to them.
25. Tradeshows - Collect business cards and scan them into a spreadsheet. Make sure you ask permission to send email to them, then mark the card.
26. Use Facebook - Host your own group and invite people to it, then post new links often. From time to time, post a link to sign up for your newsletter.
27. Use Facebook - Post the hosted link from your newsletter into Linked Items to spread the word.
28. Use Facebook - Include an opt-in form on your Facebook Fan page.
29. Use Twitter - Twitter the hosted link of your email campaign every time you launch.