Please mind the mess while I construct a properly listing of all existingAS3 Libraries/APIs:
asSQL - Connect from ActionScript directly to mySQL
corelib - The corelib project consists of several basic utilities for MD5 hashing, JSON serialization, advanced string and date parsing, and more.
FlexUnit - FlexUnit is a unit testing framework for Flex and ActionScript 3.0 applications. It mimics the functionality of JUnit, a Java unit testing framework, and comes with a graphical test runner.
Flickr - The Flickr library is an ActionScript 3.0 API for the online photo sharing application, Flickr. It provides access to the entire Flickr API.
Mappr - A service and application that combines images from Flickr with geolocational information. The Mappr ActionScript 3.0 API gives you access to Mappr’s geo-tagged image data.
RSS and Atom libraries - Use the RSS and Atom libraries to parse Atom and all versions of RSS easily. These libraries hide the differences between the formats so you can parse any type of feed without having to know what kind of feed it is.
Odeo - The Odeo API provides an ActionScript 3.0 interface for searching and retrieving podcasts from Odeo.
S3 Amazon ActionScript Classes - Connect to Amazon’s AS3 service from Apollo
YouTube - The YouTube API provides an ActionScript 3.0 interface to search videos from YouTube.