Readers from the Chicagoland area, have you heard of Chicagoland Savers? You can use this site to find coupons, but more importantly you can use it for half off dining deals. Many of the restaurants listed here offer a certificate for $50 worth of food, but you only pay $25.
As mentioned earlier, another great place to find half off deals particular to the Chicagoland area is WTMX Mix Dining deals. Both of these are a nice supplement to restaurant.com and Groupons. Works for me!