Right on the heels of Amex gift cards being withdrawn from other portals, the cash back portal hoopla doopla seems to be offering 40% cash back for Amex gift cards. If you go for this, make sure to take screen shots and keep careful records. I think the chance of this being honored is very close to zero, but the potential payout is huge.
UPDATE: I added my referral link to Hoopla Doopla here. The person who refers you earns 20% of anything you earn.
Notes about buying Amex gift cards:
1. Do not use promo codes
2. Do not pay with a Citibank card (since they will treat the purchase as a cash advance)