Amazon CTO Werner Vogels and services evangelist Jeff Barr used their blogs to announce Amazon Flexible Payment Service, or FPS, this morning.

FPS, the latest addition to Amazon's Web services, lets site developers use Amazon's payment system to charge customers for using their services.

It's dubbed flexible because it allows a variety of payment methods -- credit cards, bank account transfers and Amazon Payments -- and charges different merchant/developer fees depending on which method a customer uses.

In a particularly clever move, FPS will use Amazon's authentication system. That means customers registered with Amazon will use the same login and payment information at other Web sites using FPS. Vogels put it this way:

This helps Amazon customers keep their payment information secure while exploring new services and its helps developers by removing the typical friction associated with making a first-time or repeat purchase.

This works both ways. Web services that register new customers will add to the list of Amazon registered customers. Amazon's authentication/payment system is a long way from becoming universal, but this could nudge it that direction.

FPS also puts Amazon into direct competition with Microsoft, Google and eBay, all of which are trying to propagate their own online registration and payment systems. I wish they'd all work together so you'd only have to use a single sign-on for everything, but that's a fantasy.