Loadster - Loadster is a full-featured load testing solution for websites, web apps, and web services.
Postman - The Collaboration Platform for API Development
Loader.io - Loader.io is a simple cloud-based load testing service
Sauce Labs - Test mobile or web apps instantly across 700+ browser/OS/device platform combinations - without infrastructure setup.
LoadFocus - Cloud Testing Infrastructure | Cloud Testing Services and Tools for Websites & APIs.
TestComplete - TestComplete Desktop, Web, and Mobile helps you create repeatable and accurate automated tests across multiple devices, platforms, and environments easily and quickly.