John approached this problem in a wonderful distributed format with an application he calls TestSwarm. He created an application that allows end users to load up their browser and allow it to wait for tests that need to be run to be sent to it from the central server. So by opening up a browser window to a certain page, it polls for any work to do. If it finds something to do, it pulls the test, executes it and sends the results back to the central server. This allows JQuery to be tested easily across many OS and browser implementations and quickly find any bugs that may appear.
Kudos to John on a great application. Go check it out, sign up, and donate a couple of spare CPU cycles to the cause.