A friend of mine asked for a simple program.
Input: Coordinates of some points, spheres, planes etc. ( from an excel document (strictly) )
Output: A 3D view of the input which the user can move the camera.
The questions is, how can I do that easiest way. I have experience in C++, C#, Flash (AS), Java
This is going to be your major problem, reading an excel document from Flash is not an easy task. You will either have to process it on a server side script with XML/JSON/AMF output to the client, or simply give up on the format.
Displaying 3D objects in flash is easy using one of Papervision3D or Away3D.