I remember seeing that someone associated with Emory was working on this kind of system, but it wasn't active yet. They had a pilot program going for the area immediately around Emory and I believe they hoped to expand it to the greater Atlanta area in the next few months. But ... unfortuntely I don't remember where I saw it now.

A site that might be helpful is http://www.atlantaregional.com/transportationair/bikepedmaps.html. It has maps that show how "suitable" roads are to bike riding. It might help you put together your own routes ...