Selenium, an alternative to Microsoft’s Coded UI Tests.
Selenium comes in three flavors. Selenium IDE, Selenium RC, and Selenium Grid.
For the non programmer, there is the Selenium-IDE, which is a Firefox plugin. The plugin allows you to navigate through Firefox to verify or assert that the expected page content exists. It also tracks as you click on links and navigate page to page. You can even fill out forms. The IDE allows you to save your tests to HTML or one of several other programming languages. These scripts can then be passed on to Selenium RC. Supported languages for the Selenium IDE are HTML, Java, C#, Perl, PHP, Python, Ruby.
Selenium-RC allows you to integrate the Selenium API into your development environment. As long as your programming language of choice supports sending and receiving HTTP PUTs and GETs, you can use Selenium RC. What this means is that you can build more advanced test suites that can respond to failed tests. Being able to incorporate an API also allows you to utilize programming logic such as loops and conditional statements.
Selenium-GRID expands on Selenium RC by allowing your tests to run simultaneously on multiple browsers, dramatically speeding up large testing suites.