In the past I've been an avid Google user. That was until I heard of Bing Reward program.
You receive points for each time you search. Then you can use the points to purchase gift cards from various places such as Donors Choose, Groupon, and Amazon. I've been using it for the last year and was able to have one of my Donor Choose projects funded solely from Bing gift cards. You can sign up for the program here.