Take 10% off at best-of-breed online jeweler Blue Nile depending on the credit card you pay with. Use an American Express, Mastercard or Visa and enter code AEXP28, MCARD08 or VISAW29, respectively, in the "reference code" box. Blue Nile is the largest online jeweler, having sold over 150,000 engagement rings. They buy diamonds through the same wholesalers that Tiffany's does, but can sell for 20-40% less. They have a well-explained website (see their wedding ring guide, for example), guiding men (mainly, including myself) to an informed purchase without the sleazy salesman. FedEx Priority Shipping is free on all orders, there's no sales tax and a fully guaranteed 30-day return policy. The 10% will apply to settings but not diamonds with "build-your-own" jewelry because prices are already so low.