Ryan Erickson over at CG Information has posted a list of some establishments that offer a discount. And, I'll note that often times the discount is not advertised: at the IHOP in Ghent, they have a paper taped to the door with details on their discount; the new IHOP in Portsmouth doesnt, and I just figured the discount was specific to the Ghent store; I thought perhaps that franchise owner wanted to pay pack to those who serve. Turns out the discount is available in every IHOP.
For those who are in the Reserves or are retired, it can't help to ask. I'd just ask if the establishment offers a military discount and be ready to show my ID card. Our local Chinese restaurant in Olde Towne takes 10% every time I ask, "Do you still offer a military discount?"