I need to pick a polymer for my science project. It has to be organic and preferably simple.

Some that are already taken are: polyethene, polystyrene, PVC, polyacrylonitrile, DDT , nylon..

Thanks a lot it has been really hard for me to find something.

I don't know if you must make this stuff or just write about it. If just writing about it I should think polybutadiene would be a good one. For other ideas you might look at an organic chemistry text and look for the chapter on polymers.

I need to make 2 monomers of the molecule using styrofoam balls

That should be easy enough. It would be quite difficult to make the real stuff.