Here’s one way; I wouldn’t at all be surprised to see some much better ones.
I made this glass clear, with a sligtly wavy texture applied to the normal to make it easier to see, and to see the refaction effects. The important material settings for the glass are the Alpha, IOR, and (in this case) Ray Transparency settings. I made the glass slightly reflective. I increased the ray transparency depth to make sure that as light rays passed through the surface toward the camera then again through the part of the surface away from the camera, that it continued to show objects behind it; you may be able to use a lower setting, depending on how many glass objects you use.
I also set the “TraShadows” property of the mateial on the ball behind the glass, so it would receive lighting information for light rays that passed through the glass. I rendered this inside Blender (2.42a) using the default Ray Tracing settings and a default light.
Hope it’s useful for you.