Take a rare 10% off at best-of-breed online jeweler Blue Nile via either reference code VISAW18 (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 that will help you make 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. Their Mother's Day shipping deadline is 6pm on Thursday May 8th.