Postman - The Collaboration Platform for API Development
Django REST framework - Django REST framework is a toolkit for building web APIs.
DataEquity.io - DataEquity: The API Platform for API Governance
Amazon API Gateway - Create, publish, maintain, monitor, and secure APIs at any scale
Google Cloud Endpoints - Google Cloud Endpoints provides the tools to develop, deploy, protect and monitor your APIs.
Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing