Checkout by Amazon and Amazon Simple Pay are two different levels of PayPal-like services quietly launched on Tuesday. No press release, no front-door promo. Simple Pay works a lot like PayPal — customers at another e-commerce site can use it as an alternative to entering a credit card number. Checkout by Amazon goes further, letting websites make use of Amazon's 1-Click ordering and allowing shoppers to put purchases in the same virtual cart. Previously, Amazon had required retailers to set up on itself. Now, the company is looking to get a piece of the action any way it can.