From Amazon :
Amazon Exclusive Pre-order Treasure Map
Pre-order “Uncharted 2: Among Thieves” and get an Amazon exclusive treasure map. This bonus video strategy reveals the secret locations of treasures hidden within the game and can be viewed on both the PS3 and PSP systems. Access codes will be sent within 10 days after the game releases. Offer good while supplies last. Must be sold and shipped by Amazon.com to be eligible.