Whiten those pearly whites on the cheap! This month at Walgreens, Arm & Hammer Whitening Boosters are on sale, buy one get one free. There is a new coupon for $0.75 off one Arm & Hammer Whitening Booster. Since the Walgreens coupon policy allows a coupon to be used on a free item, print and redeem two coupons. The final price is $2.50 each!