Postman - The Collaboration Platform for API Development
WSO2 API Manager - WSO2 API Manager is a 100% open source enterprise-class solution that supports API publishing, lifecycle management, application development, access control, rate limiting and analytics in one cleanly integrated system.
Amazon API Gateway - Create, publish, maintain, monitor, and secure APIs at any scale
Tyk - Tyk is an open-source API gateway and API management platform.
Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing
apiman - Open source API management