Amazon has Crest 3d White 2-Hr Express Whitestrips Dental Whitening Kit, 4-Count for just $19.92 Shipped when you clip the $10 coupon found on the product page. Submit this $15 rebate form and you can score this kit for just $5.16 Shipped!
Remember that in order to see the $10 off coupon, you will need to be signed in to your Amazon account.