OK, with the holidays coming up, Amazon gift cards can definitely come in handy. And, right now, StumbleUpon is running a promotion through which you can earn $10 gift cards!
All you have to do is sign up at StumbleUpon, refer 5 friends (who actually sign up) and get a $10 gift card from Amazon!
This promotion runs through December 14th and you can receive multiple gift cards! But, you only get a card for every 5 people who sign up -- there is no partial credit.