Postman - The Collaboration Platform for API Development
Apigee - Intelligent and complete API platform
Django REST framework - Django REST framework is a toolkit for building web APIs.
Amazon API Gateway - Create, publish, maintain, monitor, and secure APIs at any scale
Koofr - Koofr offers safe EU based cloud storage with free storage space for life and options to connect multiple cloud accounts (Dropbox, Google Drive, OneDrive) and your personal storages.
Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing