Yesterday, I came across a third party app for Facebook that let's you add coupons to your page and has a great deal of customization available. I decided to try it out for one of the restaurants and in less than 24 hours we gave 30 coupons and added 30+ new friends to the page. One of the cool features is you can specify that the person needs to "like" your page before they can get the coupon. Check them out at Woobox.
I have been hesitant to use, or pay for, any third party apps but I'll be upgrading to a pro account for this app.