Using Selenium-RC, using the Ruby Client Driver.
Some other guys are using Watir and are able to use IRB to attach Watir to an open browser and send it commands. This has enabled them to greatly speed up their development time.
Without this ability you have to wait for several test steps to execute (such as logging in and opening the page you're writing a test for) before the test you're actually working on executes. When you have some deeply nested, dynamically written DOM elements and you're having trouble getting your XPath right, this is a huge pain! Very time consuming.
I have heard that it's possible to telnet into a Selenium server and send it commands. Any info on this or other techniques for sending commands to Selenium so I can quickly try out XPaths?