I'm part of the Bing Rewards program. Basically, Bing gives you "credit points" if you use their search engine. Get enough points, and you can turn them in for an Amazon gift card or other cool stuff.
This is the ONLY reason I use Bing. Once I've gotten my daily amount of points, I go back to using Google.
It takes about three weeks to get a $5 Amazon card. I use Amazon to buy birthday/Christmas presents for my relatives, so I'm trying to be fair and balanced. Half of the money I get goes into the present fund, and the other half goes into the "Michael buys stuff he wants" fund. The downside is that, if I want to buy something for myself that's more than $5, I have to wait a few months. So, normally, I buy a paperback Nancy Drew book that's not available at the local library.