I don't do the twitter/facebook thing. This board was my source for shift codes, but it's pretty dead now.
The link comes courtesy of another GFaqs user, can't remember the name, that posted it few weeks back. --- Wise men talk because they have something to say, fools talk because they have to say something.
You aren't required to have twitter/facebook account. You can simply just bookmark Gearbox/BL2 twitter/facebook, their shift code posts are all public. --- If you want breakfast in bed, just sleep in the kitchen
http://orcz.com/Borderlands_2:_Golden_Key (the link the previous user posted) is still good.. at the bottom of the page it has links for 11 gold keys that I can confirm work as of today (.. even the last one that says it expires on the 10th.. just worked for me.. and two of those 11 codes counts for FIVE gold keys EACH).
i just got borderlands 2 yesterday...tried the orcz site and got like 23-24 keys off of it...its kind of messy with no real expiration dates listed...but its the best i found --- (Troll-victim) Baggins: league of legends is NOT the internet