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.
mashape - mashape is a cloud API hub. It is a place to consume, distribute and manage private and public APIs. The mission is to to unlock and facilitate the distribution and consumption of data and services.
Tyk - Tyk is an open-source API gateway and API management platform.
Apigee - Intelligent and complete API platform
apiman - Open source API management
Gravitee.io - Gravitee.io is a flexible, lightweight and an open source API management solution.