Being a predominately self-taught web developer, I’ve slowly migrated towards object oriented programming and, to my credit, made some applications that work but, at the same time, those apps definitely could have been made better and more efficiently.
A couple of weeks ago, I finished reading Advanced ActionScript 3 with Design Patterns by Joey Lott and Danny Patterson and found it quite helpful. Now knowing what the MVC, singleton, proxy, iterator, composite, decorator, command, memento and state patterns are I can better utilize them in my Flash projects and ultimately make better coded apps than I could before. In addition to design patterns, the book also has a couple chapters on application design, programing interfaces, working with events, sending & loading data, E4X XML and regular expression, which offer more in-depth coverage than in other books.
In short, if you’re curious about learning more about classes and design patterns in ActionScript 3, I would recommend that you read Advanced ActionScript 3 with Design Patterns.