There are 5 to find, but the 5th one is only available starting on Black Friday and is an all black bill to commemorate the busiest shopping day of the year!!! The Black Friday Bill will be available until Cyber Monday when finding all the Thanksgiving collector bills ends and if you find all 5 bills then on November 29, 2011 you will get a bonus of 10 swag bucks for your hard work!!!
The ones I have found so far are:
I wish I could have seen what the Black Friday Collector Bill looked like though *sighs*