Blazemeter - BlazeMeter is a self- service performance load testing cloud tool
Loader.io - Loader.io is a simple cloud-based load testing service
flood.io - Load Testing for Everyone
WebLOAD - WebLOAD - The most flexible and cost effective software for enterprise load, stress and performance testing, integrated with DevOps processes. Click for details
Apache JMeter - Apache JMeter™.
gatling - A high performance web server. Small! (125k static Linux-x86 binary with HTTP, FTP and SMB support).