Take a rare 10% off at best-of-breed online jeweler Blue Nile via either reference code VISAW37 for Visa cardholders or reference code WISH07 for those with American Express through 12/31. Blue Nile is the largest online jeweler, having sold over 50,000 engagement rings. They buy diamonds through the same wholesalers that Tiffany's does, but can sell for 20-40% less. They have a very well-explained website, guiding men (mainly, including myself) to an informed purchase without the sleazy salesman. Blue Nile currently has free FedEx Priority Overnight on all orders, no sales tax and a fully guaranteed 30-day return policy.