is there a way to make light pass through glass objects, and leave just a slight shadow?
There is a thread just below yours on the same page.
http://blenderartists.org/forum/showthread.php?t=71240
You need to enable TraSha in the Shadings window (F5) on the surface the shadow is falling on. So if you have a glass sphere on a white plane, enable TraSha for the plane and the sphere now casts a proper shadow.
ok, thanks