FlashFirebug (now Flash Debugger) gives you the ability to debug any AS3 Flash on the web. Inspect the DisplayList, change properties on the fly and see the warnings, errors and traces directly in the extension. Use the inspector to hone in on elements, transform objects on the fly and use the console to run AS3 commands.

3D Transform Tool

The 3D Transform tool lets you scale, rotate and skew your objects at run-time. Simply enable the 3D Transform tool above the tree display, select an object and then use the handles on the bounding box to perform free transformation, 3D rotation and 3D translation like you would do in any graphical IDE.

While using this tool, you can see the changes reflected on the property panel on the fly.