Bob Cotton from Rally made a talk about "Testing Web Applications with Selenium and Ruby" at the local Agile Methods Users Group.
It was very good. I liked Selenium IDE, which is Firefox Plugin, with which you can record and play back user actions. It generates Selenium HTML script. And what I liked most was that you can export to Java or Ruby code (or any language Selenium supports) in the format of TestCase like JUnit.
And I liked the way they used Ruby for their tool on the top of Selenium. Even though that second section of the talk was about their proprietary tool, I learned a lot about how Ruby is used. I liked the way they used Metaprogramming and block.
Reference: http://openqa.org, RSpec