This will help flash developers more hard core in developing flash applications or games.
AS3CoreLib
Utilities for working with ActionScript 3.0
http://code.google.com/p/as3corelib/
AS3 Facebook Platform API
Actionscript 3.0 Client for the Facebook Platform API
http://code.google.com/p/facebook-actionscript-api/
ThunderBolt AS3
A lightweight logger extension for Flex 2/3/4 and Flash ActionScript 3 applications using Firebug within Firefox.
http://code.google.com/p/flash-thunderbolt/wiki/ThunderBoltAS3
Google Maps API for AS3
http://code.google.com/apis/maps/documentation/flash/intro.html
AS3httpClient
Extends the capabilities Adobe Flash Player 9 for HTTP/HTTPS related requests.
http://code.google.com/p/as3httpclient/
GoogleAS3API
AS3 library on Googles API’s, integrate the power of Google in your Flash/Flex/AIR application (searches, translation, suggest, weather, feeds).
http://code.google.com/p/googleas3api/
Twitterscript
Twitter API in ActionScript
http://code.google.com/p/twitterscript/
YouTube AS3 API Player
The AS3 API allows users to control the YouTube video players by loading the player into a Flash application and making calls via ActionScript to the player’s public API.
http://code.google.com/apis/youtube/flash_api_reference.html#Requirements
LastFm AS3 API
ActionScript 3 implementation of Last.fm’s 2.0 API
http://code.google.com/p/lastfm-as3-api/
AS3Awss3Lib
ActionScript 3.0 library for interacting with Amazon S3
http://code.google.com/p/as3awss3lib/
AS3flickrlib
Flickr ActionScript 3.0 API .
http://code.google.com/p/as3flickrlib/
AS3syndicationLib
ActionScript 3.0 library for handling syndication feeds.
http://code.google.com/p/as3syndicationlib/
Minimalcomps
Minimal ActionScript 3.0 code only UI components.
http://code.google.com/p/minimalcomps/
FlexUnit
FlexUnit is a unit testing framework for Flex and AS 3 applications and libraries.
http://opensource.adobe.com/wiki/display/flexunit/Downloads
Deface
Actionscript 3 visual object detection/tracking libraries.
http://code.google.com/p/deface/
ExactText
Measures text metrics on fonts at random sizes in AS3.
http://ileavebehind.com/news/?p=11
PaperVision3d
http://code.google.com/p/papervision3d/
Away3D
http://away3d.com/
PushButton
Game Development framework.
http://pushbuttonengine.com/download/
Flash Punk
2D Flash gaming framework.
Flash Punk
Flixel
Game framework
http://flixel.org/index.html#games
Box-2D
A 2D rigid body simulation library for games.
http://sourceforge.net/projects/box2d/
PureMVC
http://puremvc.org/
RobotLegs
http://github.com/robotlegs/robotlegs-framework
GutterShark
http://codeendeavor.com/guttershark
CasaLib
http://casalib.org/
Service Capture
Captures all HTTP traffic sent from your browser or IDE.
http://www.kevinlangdon.com/serviceCapture/
TextMate
A MAC text editor
http://macromates.com/
FlashDevelop
A PC open source code editor
http://www.flashdevelop.org/wikidocs/index.php?title=Main_Page
Eclipse
http://www.eclipse.org/downloads/
http://osflash.org/eclipse
THE HOLY GRAIL OF FLASH OPEN SOURCE
http://osflash.org/projects