A web based tool for Action Script development, available on code.google.com
Available at this site (link)
From this site:
Flash MiniBuilder is a lightweight IDE created for developing programs written in ActionScript 3.
Flash MiniBuilder is itself written in ActionScript
Two of the main raison d'etre of MiniBuilder are
1. provide a completely free and cross platform alternative for developing ActionScript projects.
2. provide an editor with a small footprint that would eventually run on smaller computers like netbooks or even pocket-size devices.
Extending, changing (and even integrating MiniBuilder with other software) is easy: MiniBuilder is itself written in your favourite language, AS3