Amazon offers Prime members the ability to earn a variety of credits for accepting a slower shipping method instead of 2nd day shipping.
Until now there has been no way to view those credits online, but Amazon has finally added a page to check on no-rush credits and to see when they each expire.
You can also view other Amazon gift card and credit balances here.
HT: troyarcher, via DDF
Amazon offers free shipping with $25+ orders or get free 2nd day shipping on all orders with a free trial of Amazon Prime.
A prime trial is also free with Amazon Family (which also gets you up to 20% off diapers among other benefits)
or Amazon Student. EBT Cardholders can save on Prime Membership here.