From Facebook Developer Wiki

Adobe and Facebook have teamed up to bring you official support for the ActionScript 3.0 Client Library for Facebook Platform. Use this library to call the Platform API from your Flash Web and desktop applications as well as Facebook Connect sites.

• Download the ActionScript 3.0 Library for Facebook Platform
• Get Started at the Adobe Developer Connection

In addition, you can make Platform API calls to Facebook using any of these community-supported ActionScript 3.0 APIs:

• Lightweight FacebookBridge for AS3
• FBAS - extension to Facebook Actionscript API