For all you Android users . . . if you haven't already downloaded the app I recommend
Google Opinion Rewards. It did not take me more than a few months to rack up over $20 in credits just by answering 1 or 2 questions a day a few times a week. I 've been using my credits to purchase publisher bargains in the Google book store. So far I've gotten 6 books for $10 in credits and still have $10 left to spend.
Well worth the (almost no) effort.