One of the cool new features in Adobe Flash CS3 is the ability to copy a motion tween from the timeline in the form of XML and AS3 code, which can then be applied to other display objects in the Flash IDE. Its also possible to save this code as external XML files which can be imported using Flash or Flex.
This is huge for Designer to Developer workflow, and will make it a lot easier to put the graphical flexibility Flash is renowned for into Flex based applications and media.

Here are some good links I came across while checking out this feature:

Motion XML Elements on LiveDocs
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/motionXSD.html

fl.motion package on LiveDocs
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/fl/motion/package-detail.html

Overview of this feature by Kevin Hoyt
http://blog.kevinhoyt.org/2007/04/25/flash-cs3-export-motion-xml/

Original post here.

Brgds,

CP