Take a rare 10% off at best-of-breed online jeweler Blue Nile via either reference code VISAW18 for Visa cardholders or reference code WISH07 for those with American Express (this does not apply to diamonds with "build-your-own" jewelry because the prices are already so low). 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.