The BlueSnap Payment iOS SDK by BlueSnap allows API communication to implement payment features into eCommerce applications. It includes a link to download the kit, along with guides to integrate from download to initialization.
When Zappos released its API, there was a strange restriction: no mobile applications. While sometimes lawyers write terms that aren't formally enforced, Zappos made it clear on its API mailing list that it was serious. Soon, the restriction will be removed and mobile applications will be allowed without written approval.
In Chicago today eBay will kick-off of their annual eBay Developer's Conference by announcing Project Echo, a way for outside developers to integrate their apps "directly onto the world's largest ecommerce site".
Sometimes we forget what the real purpose of all this fancy technology is. And what is that? To make our real lives easier. Mashups often help with that, allowing us to do such simple things as find a good beer, our favorite music artists, where the streetcars are, or where a park is.