While supplies last, American Express cardmembers can purchase a $25 American Express gift card for $15. You will, however, need a Twitter account (which you can create for free, if necessary). To take advantage of this deal, follow these steps:

Update 2/12/13: This deal has expired, as the gift cards sold out quickly.

• If you haven’t already taken advantage of Amex / Twitter deals in the past, you’ll first need to sync your American Express card to your Twitter account. You can do that by going to this link and following the instructions.
  • Note: If you are a complete novice to Twitter, you can read this post to step you through the process of creating a new Twitter account and syncing your Amex with it.
• From your Twitter account, tweet #BuyAmexGiftCard25.
• Look for a response from @AmexSync under the mentions tab at twitter.com/mentions. The response will contain your confirmation #hashtag (#ConfirmAmexGiftCard25). Due to high demand, if you are getting in on this deal early, you may need to wait a while–over an hour, possibly–before receiving the confirmation tweet from Amex.
• Tweet the confirmation #hashtag (#ConfirmAmexGiftCard25) within 15 minutes of receiving the response from @AmexSync.
• Once the purchase is confirmed, you’ll receive another response from @AmexSync at twitter.com/mentions telling you that your purchase was successful as well as an email. Your gift card will then be shipped via free 2-day shipping.

The Amex gift card can be used almost anywhere in the U.S., Puerto Rico and the U.S. Virgin Islands that American Express is accepted and has no activation fees and no inactivity or service fees.

You can find the full terms of this offer here.