Ending today, Groupon offers a $40 Google Express Credit for $15 for new customers only. (This offer is valid only for the DC area. Check availability for your ZIP code here.) Coupon code "SALE3" cuts the price to $12. That's $3 under last month's mention, $28 savings, and the best deal we've seen for a $40 Google Express credit. Google Express is a delivery service that allows you to order from local grocers and retailers like Walgreens and Costco. Voucher expires April 1.