API List - A collective list of APIs. Build something.
Postman - The Collaboration Platform for API Development
Interspect - Test the data you send to Microservices & APIs
Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing
TelstraDev - Telstra's home for all things API and developer
Django REST framework - Django REST framework is a toolkit for building web APIs.