Run contests on your website (or include surveys and polls) to grab opt-ins for your newsletter then put your new subscribers to work for you.

A contest at your web site works on the same principle as signing up for a contest to win a free dinner at a local restaurant. Both parties get something of value (you get their contact information and they win a prize). Make sure that the registration for this contest is SIMPLE. Your visitor should not have to spend more than a minute or two to complete the task