Particles
From the site:
Particles is a class that manages simple MovieClip motion. Obviously by it’s name it can be used to create particles such as falling snow, leaves or anything else. And the MovieClips don’t have to fall. They can also float up.
 http://polygeek.com/452_adobeflash/actionscript_particlesÂ
Random Methods Utility Class
Simple collection of utility methods for working with random values.http://www.gskinner.com/blog/archives/2008/01/source_code_ran.htmlÂ
Swinger
Swing a movieclip on an axis point.http://pixelfumes.blogspot.com/2008/01/swinger-class-with-source.htmlÂ
MouseControl
From the site:
MouseControl class for now just takes care of Mouse scroll wheel capability in Flash MouseControl is Singleton class which lets you define movieclips and functions that should be invoked if user uses mouse scroll wheel over defined movie clip.Â
 http://mrsteel.wordpress.com/2008/01/27/373/Â
as3httpclientlib
HTTP/HTTPS client library for Actionscript 3.From the site:
The goals for this project are:Learn the HTTP protocol by actually implementing it.Use AS3Crypto TLSSocket support for implementing HTTPS.Use it as a replacement for Flash’s URLRequest/URLStream API.Support the Flash and AIR runtimes.
http://code.google.com/p/as3httpclientlib/
LetSnow Flash Snow Effect Component (as3)
LetSnow Flash Snow Effect Component (as3):
LetSnow Flash Component Info
LetSnow Flash Component is a standard extension for Adobe Flash CS3. You simply install the MXP file and then you just drag & drop the extension from the Components panel onto the scene of your movie. The component can be used in a movie with any structure. You can control the component to create snow effect.
Component Features
We have built our component to be easily customizable and easy to use. You can set the size of the snowflakes, the power of the wind, the amount of gravity, and many other parameters.
Online Demo:
http://www.letsnow.net/demo.html
Documentation (parameters):
http://www.letsnow.net/documentation.html
AnimatedBitmap
From the site:
The AnimatedBitmap class provides functionality for Bitmap objects that are animated by using a series of still images. When creating a new AnimatedBitmap you provide a BitmapData object that contains an image that consists of the ’single-frame’ images for the animation.
http://labs.hexagonstar.com/animatedbitmapclass/
StringTokenizer
From the site:Â Â
One useful utility in the java.util package is the StringTokenizer class. I was looking for an ActionScript implementation the other day but was unable to locate one. So after determining the level of effort to write a StringTokenizer in ActionScript was minimal, I decided to roll my own.The ActionScript StringTokenizer is a convenience class which provides a simple mechanism from which Strings can be extracted into individual tokens based on a specific delimiter.
http://www.ericfeminella.com/blog/2007/11/01/as3-stringtokenizer/
FrameScriptManager
From the site:Â Â
I recently built a simple class called FrameScriptManager that allows you to set actions on any frame referenced by number or label at runtime from within a bound class. This allows developers to associate code with specific points in timeline animations or transitions, without having to modify the FLA. Because you can reference frames by label, the developer also does not have to worry about designers changing the length of the animation, as long as the label remains in the appropriate location.
http://www.gskinner.com/blog/archives/2007/11/replace_actions.html
Inflector
The as3 Inflector class can be used to pluralize or singularize most words. It is essentially a direct port of the Rails inflector class.