AmazonLocal often has good deals and free vouchers available!  Right now, you can find one for Burger King.
This appears to be available when you look under various cities (I found it under Birmingham), but it isn’t under the “National” deals on AmazonLocal.

More details:

• Free voucher for one WHOPPER® Sandwich with purchase of a WHOPPER® Sandwich
• Free voucher for one WHOPPER JR.® Sandwich with purchase of a large French Fry
• Dress your WHOPPER® Sandwich up with mayo, onion, pickles, ketchup, and more
• Crisp, tasty French Fries complement the WHOPPER JR.® Sandwich perfectly

• Voucher will expire if not used by July 15, 2013
• Customers must take printed voucher in to redeem; vouchers displayed on mobile devices will not be accepted
• Available for use at participating BURGER KING® restaurants only. Click here to find an eligible location near you
• Limit 1 voucher per customer per option
• Only 1 voucher may be redeemed per visit
• Voucher only valid for option purchased; cannot be redeemed for other menu items
• Sales tax applicable
• Not valid on specialty versions
• Not to be used with any other coupons or offers
• Offer is not transferable, not exchangeable and has no cash value
• Void where prohibited
• Voucher is available for use immediately after purchase