Selenium
SELENIUM is the largest open source automation project around today. Not known for it’s simplicity to implement but fast gaining ground as the tool of choice for automating web testing. Not great for anything other than web testing mind you as it doesn’t support anything other than web technologies.
JMeter
The Apache JMeter™ application is open source software, a 100% pure Java application designed to load test functional behaviour and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.
Cucumber
Cucumber is a software tool that computer programmers use for testing other software. It runs automated acceptance tests written in a behavior-driven development (BDD) style.
Gatling
Gatling is an open source load testing framework based on Scala. As the first protocol module of Gatling, Gatling HTTP allows you to load test web applications, web services or websites. It supports HTTP and HTTPS with almost every existing features of common browsers.