FlashKit.com
AS2 to AS3
ActionScript 3 Design Patterns
Kirupa.com
ActionScript.org
Flashguru.co.uk
AS3 Variables
AS3 Defined
IT Definitions
Object-oriented-ActionScript
Flash Tutorial
Misc. Flash/PHP scripts
Wikipedia AS

Flash Samples

Flex/Ajax Bridge
Flex 2 Component Explorer
Flex and AS3 Tools, Libraries and Components
PureMVC Framework
Better Flex and AS3 unit tests with Behavioral Mocking