If you want to go to ActionScript 3.0, then this overview of the main libraries, resources, and all that you need to learn and work on ActionScript 3.0, especially for you. Migrate!
ActionScript 3.0 Libraries - a set of free and open libraries, such as eBay, FlexUnit, Flickr, Mappr, Syndication library, Odeo, YouTube. Posted by: Mike Potter
AS3 Crypto Library is a library that implements basic cryptography algorithms. Posted by: Metal Hurlant
AS3 Lightweight Remoting Framework is a simple but functionally powerful framework that provides control over remoting (remote) calls. By Danny Patterson
Asql is a library for direct connection to MySQL databases. Can be used in Flex, Apollo and Flash CS3. Posted by: Łukasz Błachowicz
FZip is a library that can download ZIP archives, followed by unpacking and decompression of attached files. Authors: Claus Wahlers, Max Herkender
Papervision3D is a smart enough 3d engine for Flash 8 and Flash 9. Authors: Carlos Ulloa, John Grden, Ralph Hauwert
Yahoo!AS3 API Libraries is a toolkit that provides access to Yahoo resources. Posted by yahoo
Utilities
as3converter AS3 - converts AS2-projects to AS3. I note that realistically, as3converter will not be able to convert your projects correctly, but it does some of the routine work by
FlashDevelop is a free editor, with check and support for AS3 syntax. Compilation of projects is carried out through the free mxmlc compiler.