Thursday's USA Today had coupons for free Mars candy and was advertising the promo. If you have access to last Thursday's USA Today, the coupon is on page A5. I had 20 extra papers that day, and the free Twix bars are great on the run.
Here's a hint for budget boarders, USA Today is becoming a good source for completely free items, but you never know when they will appear. I've had everything from free Fazolis spaghetti to Quiznos subs to 7 UP 2 litres to Powerade, Coke, and Energy drinks over the past year courtesy of USA Today.