JMeter - A very handy tool

I suppose some techies will laff when they read this, but I'm getting a first-time intro to JMeter and it's COOL! It's an open source tool, from Apache, which allows the test engineer to codify HTTP and other protocol requests, issue them to a test server, save the responses, and validate them vs. one or more assertions. Since it's written in Java, it runs on Windows or Linux nicely, too.

The UI is a little clunky and you have to make sure to Save your configuration changes before starting a run (it doesn't prompt you to do so), but it provides a lot of testing capability and flexibility.