Flash Developer Center
Yahoo! Maps AS3 API 
The new Yahoo! ActionScript 3 & Flex Maps APIs.
Featured Application: Aquarium
To see a live example please install the latest Flash Player from Adobe and ensure that JavaScript is enabled.
A fun application using ASTRA components.
More: Aquarium
Flash Theater
A screencast on Yahoo! ActionScript 3 Maps.
Other: Charts, AutoComplete and TabBar
Articles
On Flash and Flex:
Welcome Flash Developers
The Yahoo! Flash Developer Center is an ever growing collection of Flash tools, resources and information, all freely available for your use. Check back often for updates, and join the ydn-flash Yahoo! Group to exchange information with Flash developers just like yourself.
YDN-Flash Yahoo! Group
Join the ydn-flash group to connect to other developers like you and send comments and suggestions (and even bug reports!) to Yahoo!'s Flash Platform team.
problem with Yahoo Tree Component for Flash CS3
Re: Yahoo Maps: Problem removing custom overlay
ASTRA: ActionScript Toolkit for Rich Applications
ASTRA, the ActionScript Toolkit for Rich Applications, is a collection of Flash and Flex components, code libraries, toolkits and utilities developed by Yahoo! for ActionScript developers. These libraries available under the terms of the open source BSD license.
Flash Components 
Yahoo! offers the ASTRA Flash components to complement the existing set provided in Adobe Flash CS3. These components are easily skinnable and fully documented, and wide selection of examples are available to help developers get started quickly.
Components:
Resources:
Flex Components
Yahoo! offers the ASTRA Flex components for use in your Adobe Flex 3 applications. These Flex components are designed to work like any other components for Flex with familiar properties, styles, and events. They're fully documented, and each component comes with multiple examples that demonstrate its various uses.
Components:
Resources:
Utilities Library
Yahoo! offers the ASTRA Utilities for use in any ActionScript-based project, whether in Flash CS3 or Flex Builder. These utility classes build a foundation for more advanced functionality in Rich Internet Applications that is portable across different frameworks and component sets.
Components:
Resources:
Web APIs Library
Our Yahoo! Web APIs package for ActionScript 3 and Flex allows you to connect your application to any one of a variety of data services provided by Yahoo!.
Examples:
Resources:
Badge Kit
The Badge Kit is an XML-based framework for rapid development of small interactive Flash applications. You can learn how to use the Badge Kit very quickly, and most of the usage scenarios require no knowledge of Flash.