I have one key from this giveaway: Massive AddOn Author Cataclysm Beta Key Give-Away! - WoWInterface
It is a key that you can just enter into your battle.net. You must have a working wow subscription for it to work as far as I understand. I haven't traded anything on this site before so I don't know if things work differently than on other sites.
Here is a screenshot of the page for proof:
I'm looking for around 150$ negotiable. If anyone wants to act as a middleman that would be great.