This is the official Python library made for Shopify users to access the admin functionality of their accounts for use in building 3rd party applications. It was developed and is currently supported by Shopify. It provides a similar interface as does the Shopify Ruby Gem. All API usage happens through Shopify applications; shop owners can create applications for themselves through their own admin. Developers are given functionality across articles, assets, customers, events and more. The API uses a RESTful interface and responses are formatted in XML and JSON.
Blippy and Swipely both launched fairly recently with the hopes of making spending a social experience. Both services are very similar in that they both allow you to connect your bank and credit card info, as well as other accounts like iTunes and Amazon. After you've set everything up, as you start spending, you have the option to share these purchases with everyone. And now you can extend that sharing with the Blippy API.
Based in Vancouver, BC, Payfirma has created an XML-based API that promises custom forms and full shopping carts to keep you in control of developing the flow of your credit card processing. The idea is to make business's lives simpler by reducing development costs with the Payfirma API that accepts Visa, Mastercard, Discover, and American Express among others.
Shopping isn't necessarily particular for this audience, but have you ever tried to help your parents or non tech-savvy friends try to shop for a computer? SalesClark aims to combine several online shop APIs (such as Amazon and Commission Junction) to build a tool that you can sit your mom down with and help her find a computer.