Imagine two opaque plastic spheres with small light bulbs inside of each that aren't too bright. They should both emit light, but also be partially illuminated even more by the light emitted from the other one. So, hiding one of the spheres should make the other less bright and vice versa. I would prefer to use the Cycles renderer.
It seems like I can only choose between using emission or diffuse material.
P.S. I'm a newb at Blender but know the basics.