FlashDevelop

I just discovered a cool, open source tool for creating Flash (without Flash) called FlashDevelop. It is for folks who prefer coding to the Flash timeline. The UI for working with a project is very good, it is similiar to Visual Studio. You can view a project in class view, where each class shows what it extends, imports, its methods, and properties. It makes it very easy to jump around in a class or even jump up the inheritance heirarchy to look at the method stubs of the parent. The code completion works for the classes you create and for other classes you import(like Tween). It uses MTASC as the compiler, which can help catch errors.

Give it a try. Here is a good introduction to the tool at flashmagazine.com. You'll appreciate it even if you only use it as an editor for ActionScript (and not for the entire development of a project).