Grant Skinner has posted the first in a series of articles on understanding the garbage collector in the Flash Player’s virtual machine. From the first article:
Over the next few weeks (or even months), I will be writing a series of articles on this topic. I will look at the underlying mechanics of the Garbage Collector, discuss the problems you are likely to face, examine the new tools available to you for handling resource management in AS3, and offer solutions/code to help you circumvent many of the common problems you will face.
You can view the entire article here.