I will list these last two sites together as they're very similar.
E-Rewards (www.e-rewards.com) and Valued Opinions (www.valuedopinions.com) are both sites where a person can respond to surveys (much like the ones listed on Mechanical Turk) for pay.
However, rather than receiving your pay, you cash in your earnings toward gift cards, magazine subscriptions, Amazon gift cards (only on Valued Opinions), restaurant gift cards, and more.
Like Mechanical Turk, this site can be useful while waiting for emails and other bits of downtime.
You are only paid for your time working on these surveys if you actually finish the survey. If you get kicked out of the survey for not answering a question they way the survey maker wants, you either get a small amount of how much the survey would have been worth (E-Rewards) or nothing (Valued Opinions).
Before most of the surveys, there are questions that help the system figure if you're worthy of taking the survey.
Not all of the surveys are just text based. Several weeks ago, I started a survey about toilet paper. Toward the end of the survey, it asked for my address so that I could test some new kind of toilet paper. I was very happy when those sample rolls came in the mail as I was planning on buying a pack of toilet paper that day. Because of that survey, I was able to put off that purchase another week and was able to make a few dollars on the survey.