libsas is a Python library to take the pain out of using SaaS APIs. It provides an abstraction layer on top of various APIs, taking care of constructing the URLs, serializing parameters, and authentication. You just call Python methods and receive Python objects. It's like an ORM for SaaS.
PayPal Payments Pro/Adaptive Payments PHP Class Library includes methods to easily integrate all of PayPal's APIs, including PayPal Payments Pro and Adaptive Payments. It makes it extremely quick and easy to tie PayPal into your applications. It comes with template solution files for nearly every API call available. All you have to do is populate the request parameters, and you'll get a PHP array result which includes everything you'll need from the API call.