LoadFocus - Cloud Testing Infrastructure | Cloud Testing Services and Tools for Websites & APIs.
Apache JMeter - Apache JMeter™.
Loadster - Loadster is a full-featured load testing solution for websites, web apps, and web services.
Apache Benchmark - ab is a tool for benchmarking your web server.
Loader.io - Loader.io is a simple cloud-based load testing service
Tsung - Tsung is an open-source multi-protocol distributed load testing tool.