That works...yea!  Last night I tried this but had the black/white backwards...ugh.  Thank a LOT!  :)

So now I have that working, I see that I need Multi-channel versus Flat Mapping to get the Light Through Transparency working for a correct shadow.  Works...yea!  :)

That leaves the Point At modifier.  That works, but to keep it from looking up in the air, I set a Ball Joint constraint.  Is that the correct method?  (what is odd, is that for the ball joint constraint, if I lock X and Z, that locks the actual object rotation of X and Y?)

That leaves a final question related to the Shadow.  Is there a way I can have the shadow always act as if the billboard if facing the light, but have the object itself face the camera?  In that way, if I look at it from the side, I see the tree, but the shadow is appropriate.

Thanks again!