If you play in web-app testing field, then you might have heard about Selenium. It's basically a testing tool designed for web applications and it has been around for some time. I first noticed it's presence around 2004 when i was working in Jakarta. At that time, i went to an event called JAX Asia and that's when i first met Selenium.
Since then, i have been using it for my personal project and also for my teaching material when i'm teaching for testing processes. It's really a great tool.
The good news is that now they have released Selenium 2.0 which basically a major upgrade which brings many interesting features, such as modern browser support (IE 9, Firefox 5), new WebDriver APIs for Python, Ruby, C#, and Java. I believe this could enrich Selenium base support to even more programming language in the future.