Just saw this on Facebook: Amex is running a promotion where you can link your Amex card to your FB account, and then get a statement credit for meeting certain spend minimums at various merchants.

One of the merchants is Sheraton hotels, and it says that you can get a one-time statement credit for spending over $100 at Sheraton hotels (through 8/31).

Visit facebook.com/americanexpress to link any Amex card and then add the Sheraton deal to your card.

Update: there's a similar deal for Westin as well