Must use a Citibank Mastercard:
https://online.citibank.com/US/JRS/portal.c?ID=CitiWallet-For a double-dip, go through mileage/cash back mall - (e.g., Newegg.com via Chase UR mall - can buy various merchant gift cards at Newegg.com, too)
Terms and conditions:
* You will receive a one time statement credit after you make your first purchase of $25 or more and checkout using Citi Wallet with a Citi branded consumer MasterCard by 09/14/14. In order to qualify for this offer, the account must be open and current at the time the statement credit is applied. If your account is closed for any reason, including if you convert to another Citi product, you may no longer be eligible for this offer. Statement credit will be applied within 2 billing cycles.