For those of you who are using YUI 2.x or plan to be, you may want to pickup a copy of my new book Yahoo! User Interface Library 2.x Cookbook. Using detailed examples, the book explains how to use most of the components of the YUI 2 library, only excluding a couple of the recent Beta components. It is available in both print and ebook formats. Check it out:
Here is a sample of Chapter 3: Using the Event Component.