Go to Coldstone's website, sign up for their birthday club, and you'll get a coupon for a lot more than just a single scoop on your birthday.
Hell, hit Google sometime, do a search for 'free food on your birthday' and go sign up for everything you can that's in your area. On my birthday I don't pay for nothin' but tips - and I'm a great tipper too. Been having Black Angus steak dinners the past 5 years, planning on it once more at the end of May when that birthday rolls around once more.