Try eBay.
You will need to uninstall it from your machine.
Mark
I apologize for my awful english, at the beginning of 2011 I had to change my job, I was a 3D freelance designer. I would like to know if is it possible to sell my original copy of 3D Studio 2010 and the subscription update 2011.
Some hints?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic