VisibleArea has documented all As2.0 classes. An excellent source for quick reference.

MXI File Creator is a Windows Desktop Application, built with Screenweaver and Macromedia Flash MX, for creating and editing Macromedia Extensions (.mxi files).

Features:

1. Supports MX2004 Extension types (Behaviors, Commands, etc..) and File extension (.jsfl, .wsc, etc..) (version 3.0.0)
2. Specify a projects file's File Package, used for Classes and Components (version 3.0.0)
3. Add your own License Agreement, manually or import from a text file (version 3.0.0)
4. Open existing MXI files for editing
5. Add project files through drag and drop
6. Right click contect menu (Edit with MXI Creator) for .mxi file editing
7. Convert to .mxp with Macromedia Extension Manager (version 2.0.0)
8. File menu and keyboard shortcuts for common tasks: New, Open, Save, Save As, Preview, Package, etc...
9. Preview MXI file (xml) in browser
10. Includes MXI file format documentation (.pdf)

gSkinner has announced an update on the much awaited GLIC (gskinner lightweight interface components). These are light weight Flash MX2004 components with following features:

1. 75% smaller filesize than Macromedia's v2 components
2. much lower CPU usage
3. simplified skinning system
4. advanced tabbing management
5. effective, understandable code architecture
6. Flash Player 6 compatible
7. enhanced tabbing management
8. improved event model
9. polymorphic with v2 components, no learning curve.
10. In most cases, v2 components can be seamlessly replaced with glic with little or no additional modifications

Read more about GLIC here: GLIC announcement

Ladislav Zigo has great Movieclip Tweening Prototypes.

I especially loved his online Custom Easing Tool.