Marc D Anderson released a new jQuery library to work with SharePoint Web Services. The library at its alpha state, provides already 5 operations and a utility function to display cascading dropdowns. Actually the function works fine if there are less than 20 options in the dropdowns due to SharePoint behaviour, this should be fixed in future versions :

Right now, the function works only if there are fewer than 20 options in the dropdowns. As many of you know, for some reason SharePoint changes the control it uses if there are 20 or more options. We'll get that logic into the function soon, but we wanted to get this out there for folks to bang on.

Since Marc is actually looking for test swarm, you should check the latest mozilla labs TestSwarm by John Resig. Thanks to TestSwarm.com, jQuery is now being tested against 50 browsers on 9 platforms, on every commit - according to John. Pretty much insane isn't it ? There is also Selenium and JSTestDriver.

You can download jQuery library for Sharepoint Web Services from Codeplex, demo available here. Released under a MIT license by Sympraxis Consulting LLC.