DConsole is a combined logger/command-line interface for Flash 10 ActionScript 3 developers. It works as an easily-implemented layer that sits on top of your application, using introspection techniques and specifically exposed methods to grant you run-time access to your ActionScript, as well as a flexible trace message output window.
It also comes with a minor suite of graphical developer tools for simplifying common Flash developer grievances, such as making run-time visual adjustments to the application frontend before committing them to code.