Editing ActionScript within Dreamweaver MX
Dreamweaver MX is already a pretty good tool for editing external ActionScript files. Not only does it color code the files, but also adds code hinting.
Waldo Smeets has just released an extension that makes it even better. The Dreamweaver MX extension makes the Flash MX ActionScript reference panel available within Dreamweaver MX.
You can find more info, as well as download the extension here.