Right now on Amazon, you can get a 2 pack of 50 oz. Era Laundry Detergent for only $5.64 (that includes shipping!) when you select the Subscribe and Save option. I usually just select the longest time period (6 months) so that I have plenty of time to cancel the subscription! This price can change at any time and these kinds of deals usually don't last long, so stock up quick!
See offer here.