An interesting new venture called Power Gift. It is a marketplace for gift cards. You can sell gift cards you have been given, swap them for others you find more useful or even buy discounted gift cards.
They guarantee transactions and cover shipping fees for secure sign on delivery postage.
At the moment they have a $50 Marbecks card for $37.50 and a $132.94 Westfield card for $120. Looks some good bargains to me.