Flash has always been a compromise when it comes to 3D. Importing three-dimensional objects was always a matter of faking it with image sequences rendered from 3D programs. But with the arrival of Papervision3D that's all changed - real-time 3D in Flash CS3 is finally possible to achieve.
Papervision's workflow is pretty straightforward. You start by creating a low poly-count model in 3ds Max, Maya or Blender. You then use the Collada plug-in to create a file that contains information on your 3D model's set-up, textures and animation. Finally, you can use the Papervision component to import your 3D model into Flash CS3.