While Amazon.com as a rule doesn't participate in shopping portals (their partnership with Hawaiian Airlines' online mall ended earlier this year, but purchases only earned 1 Hawaiian mile per dollar, so it was no great loss), it's long been known that the Citi Forward card, which offers 5 ThankYou points per dollar spent at bookstores, would also bonus purchases made with Amazon.
Last quarter I selected bookstores (along with charity) as one of my bonus categories with the US Bank Cash+ card, which gives 5% cash back in two categories of your choice each quarter, and made a little over $100 in purchases at Amazon to see if US Bank would treat these purchases the same as Citi. And sure enough when my statement closed today, I saw that for $126.95 in Amazon purchases, I had earned $6.35 in cash back:
Although both the Discover More/it and Chase Freedom are bonusing Amazon.com purchases this calendar quarter, this is a great option to earn 5% cash back at Amazon during the rest of the year. And if you spend less than $1,500 on Amazon purchases, you can earn the rest of your cash back through bonused Kiva loans.