Ebook: Learning ActionScript 3.0: A Beginner's Guide

This is a great introuction to Actionscript 3. It is easy to follow and steps you through the language in a very logical and easy to read and understand way. As an actionscript 2 user, I found this to be incredibly useful. Particularly useful is the way that the book will teach you something in long-hand first, then take the time to explain what every part of the code is doing before making suggestions on how you can start abbreviating your code.

A fabulous resource, only bested by the Friends of EdFoundation Actionscript 3.0 Animation: Making Things Move!, AdvancED ActionScript 3.0 Animation series.