dxf would probably be the most open format for you to post. I don't know if AutoDesk does obj?? Does it? But for other AD users the dwg format would be best. I would say make a zip with dwg and dxf, post it under dwg and in the comments note that a dxf format is included (and an obj if possible). That would make your upload accessable to the most people.

 Welcome to ShareCG and thanks for sharing.

I don't fear God anymore. Anything he/she can do to me now is only adding insult to injury!