I think this is the first 'posterous' exclusive discount I've heard of yet.
Reggie Soang (who has a totally amazing food blog) has started a new brand of healthy food products called iFS, and he's giving everyone a 10% discount if you type the 'posterous' code into the checkout.
I know I'm going to buy some -- $8.95 for a 1 lbs. bag of delicious granola from a guy who really knows food and nutrition looks like a great deal. =)