If you work on flex project, you should read this.
Flex SDK coding conventions and best practices
This help a lot for building quailty code.

APE Physics tutorial for actionscript 3

APE – Actionscript Physics Engine tutorial – Part 1
APE – Actionscript Physics Engine tutorial – Part 2

Exploring the ActionScript Physics Engine in Flex

Today i bring you some cool tutorials, tips and examples about PureMVC. If you don’t know what this framework is, we can describe it in a simple way as a framework that enable developers to build modular applications in Air, Flash and Flex. What means modular applications? You build an application divided in several small [...]

Great example by “Grant Skinner”, showing how to create tree by using recursive algorithms. The source is also available for download.
Read full article and download source

Do you want to create your own flex component? Or you simply don’t like the style of the component you need to use, or even there are some features you would like to have in your actual component? The following 5 tutorials will show how to achieve these goals.

With the new version of actionscript (AS 3.0), we have assisted to awesome works on particle systems. Here i show you some of the best tutorials, articles and resources that will help you to became an ace on producing this Flash “Special Effects”.
Tutorials

Creating a particle system in Flash may sound difficult, but as Seb Lee-Delisle [...]

The latest tutorial at The Tech Labs, this time performed by Stéphane Schittly. In this tutorial, you will learn how to integrate photos from Flickr in your Flex application, using as3flickrlib.
View Tutorial and download source files

This is a nice article with source available writen by Andrew Trice, showing a cool filter effects created with PaperVision.
Read Article and check source

A great article at The Tech Labs, by Ben Pritchard from PixelFumes, that will step you through the classes used to achieve a card flipping effect using the new rotationY property that exists in Flash Player 10.
Read full article, see the demos and download support files.

See Lee Delisle has posted the sources of the his famous particle systems. They are purly awesome. Check the source code and develop your own particle systems or integrate it in your projects. I would loave to see them, so feel free to drop a comment pointing the url of your works.
Download the sources here