I’ve recently released the first version of my jQuery Cascading Dropdown plugin. You can find it on my Github page located here:
The plugin allows you to implement a cascading dropdown using multiple select boxes in which one select box depends on the input from one or more separate select boxes. Once one or all (depending on the configuration) required select boxes contain a value, it will trigger an event that will fire off the dependant select box so it will fetch its own list.
It’s free to use, so feel free to download it, use it, even abuse it, as long as you keep the copyright info intact.