Rembrandt 2-Hour Whitening Kit

Amazon.com has the Rembrandt 2-Hour Whitening Kit currently on sale for $10.41.

To get it for $7.35 with free shipping:

login into your Amazon.com account;
clip the $1.50 coupon that you can find on the product page;
use Subscribe & Save to checkout (can cancel at any time, details here).

It typically sells for $31.80, thus bringing this bargain to 76% under the retail price, saving you $24.45.