AsWing is an Open Source ActionScript 2.0/ActionScript 3.0 GUI framework and library. Its a UI centric library, and is similar to Java Swing in implementation. You can either use this library to build your application, or get only what you need.
Here is the link: AsWing
Here are some applications built using AsWing of which the Flash Mini Builder is an interesting project.
Robotlegs is an AS 3.0 micro-architecture (or call it framework) to use with your AS 3.0 or Flex Projects. Its just an extension of PureMVC and adds Dependency Injection to it. Didnt try it personally but says it reduces the amount of boilerplate code to be written to setup a PureMVC application. It also avoids Singletons and static constants from your projects. It supports Modules (It has to, as PureMVC does it).
A well accepted flash and flex framework library. The library eases the large application development head ache. It can be used for both pure AS 3.0 projects and also Flex projects. A Multicore version supports communication between modules an easy affair (again both Flex and Flash)