One of the ActionScript 3 libraries that I use in just about every project I work on is the as3corelib library. This is an ActionScript 3 library that contains a lot of useful APIs for working with AS3.
I am planning to do some more work the library this week. I spent the morning scrubbing and fixing some bugs, and plan to fix more issues, as well as generate new docs and a new SWC.
So, if you have any bugs, issues, or feature requests for the library, please log them on the project site as soon as possible.
If you have questions about the library, then check out the as3corelib mailing list.