Davide Restaurant in the North End posted a great coupon on Facebook awhile back for $25 off your purchase when you spend $50 or more. This does not include alcohol (food only) and is for dine-in only.
This printable coupon for Davide Restaurant is valid until Monday, January 14, 2013. You may also want to check on Groupon (referral link) because they did have a $40 for $20 voucher on there. However, you cannot combine offers, so pick the one that works better for you.
Have you been to Davide Restaurant before, and have you been after they were on Kitchen Nightmares? How was it?