Blogna.org is sharing a list of 30+ open source Actionscript 3.0 Libraries that might be useful for you. I believe you should know most of them however you might find some not so popular that will help you with your projects.

webresourcesdepot.com has posted 10 actionscript libraries / classes which are not so famous has Papervision, Flare and others.

These are also very useful and you will for sure enjoy to meet some of them.

The list includes:

Playr (AS3 music player class)
flXHR (Flash solution that mimics Ajax by a XMLHttpRequest compatible interface)
KitchenSync (focused on sequencing animations and other time-based actions)
AnimationPackage (AS3 library for creating powerful, maintainable animations and primitive shapes)
Flint (Flash library for creating particle based effects)
AsWing (making Flash application UIs easily)
ActionScript Page Flip Class (create the famous page flip effect)
ASZip (zipping with Flash)
FZip (loading, modifying and creating standard ZIP archives)
AS3Crypto (cryptography library that supports common algorithms like AES, DES, MD5 & more)