At Snellville Publix stores through Wednesday, you can get a BP or Shell gas card with a face value of $50 for $40 plus tax.
BUT you must get the coupon that's in the weekly sales circular. Look for the sales flier near the front doors of the store.
Some stores (or perhaps all) are limiting to 2 the number of gift cards you can purchase in this deal, and you need to have the actual coupon.
UPDATE: Hubs told me when he used the card at the gas station (in our case, Shell) it was as easy as using a debit or credit card at the pump. So, if you have been concerned that it would be extra trouble or inconvenient, it's not.