Depends on what you mean by 3D
If you only want to distort planes (like a video or sth.) that can do Flash since CS4 itself.
If you mean by 3D content: Eye-candy like rotating objects etc. I would go for erains swift3D,
papervision is also available but not easy to handle (you must know sth. about actionscript and e.g. how to create an uv-map for your models)
If you come from a 3d Background and want to create sth. like a game with lighting and cameras forget about flash and try unity3D