I been interested in the MVC design pattern for some time and will now attempt to document and create links my knowledge.
I originally created a MVC framework closely following the Mook MVC pattern in Essential ActionScript 2.0.
A working example can be downloaded at: MVC Clock.
There seem to be many more AS3 versions of MVC, varying in complexity.
The O’Reilly Essential ActionScript 3.0 by Mook provides an example using a Composite Pattern. A PDF of the MVC chapter can be found at the Adobe devnet site.
Also there is an open source framework called Pure MVC, which provides the framework in a variety of programming languages, including AS3.
There are various tutorials for using Pure MVC see: hubflanger
