See how the new JavaScript APIs and ajax framework in Drupal 7 allows you to implement dynamic behaviors without having to register a menu callback in the menu system or to write any jQuery code.
Create dependencies between form elements so that you can show/hide or disable/enable one form setting based upon the form state of another from setting.
Go on a brief tour of other jQuery and JavaScript-related contributed modules that are worth knowing about.
Jquery Overview
FreeProvides a high-level overview of jQuery to people who are brand new to this JavaScript library.