For those interested in trying out advertising on Facebook here is a coupon code for $50: JXEP-30TN-VM0J-WYCN
This may only work for a few weeks, so be quick.

Another one that is available for a long time and will probably continue to work is the Visa Business Network. Log into Facebook and add the Visa Business Network App. Once added, Facebook will send you a coupon code with instructions on how to add the credit to your account. Be sure to use the same email address for both! Use the Visa money only to promote your own business or your Facebook account will be closed!