"As developers, we have more and more JavaScript libraries to choose from and, of course, the option not to use any at all. Over time, we each tend to favor one method of coding over another. For those who’d like to learn more about jQuery, one of the more popular libraries, here’s a crash course written with code-savvy web designers in mind."
The AJAX Libraries API is a content distribution network and loading architecture for the most popular open source JavaScript libraries. By using the Google AJAX API Loader's google.load() method, your application has high speed, globaly available access
jQuery UI provides abstractions for low-level interaction and animation, advanced effects and high-level, themeable widgets, built on top of the jQuery JavaScript Library, that you can use to build highly interactive web applications.