For a GM Workshop:
I think just a time, then a request forum to see who would want to join, it would be for any GM/DM's out there. We would just kind of discuss the way each of us does things, because I can tell you no two GMs are alike, we all have our own styles. But this does little to help totally new GMs, for that I would think a few classes, might just be more beneficial. Say a couple of Experienced GMs hold a two hour class, unrelated, the new GMs get the prospective of more than one GM. This way I would think they would get the best of mulitple worlds. It might not be a bad idea to break it down into Game Systems, Pathfinder and D&D 3.5 are very similar, D&D 4E is quite different, and of course there a number of other systems out there as well.
These are just a few thoughts I had.....................