[support] dependent dropdown without ahah

How can I create a list of dependents dropdowns, for example Service > Category > User > When I select some Service, the category list refreshes the values to match with the Service selected and with users work too. I want to do this with jQuery, and I don't found any example or tutorial with full functionality. I found this, but I haven't access to this URL :( http://code.google.com/p/jqueryselectcombo/ thks in advanced