I do surveys on MySurvey as well as eRewards. MySurvey gives you points for completing surveys, and you can redeem the points for cash or merchandise. It takes 1000 points to get $10 in cash. I recently cashed in 5000 points for a $50 check that I received via mail. It took about a year and a half to accumulate that many points, but I frequently used the points to enter online raffles or donate to charity (other options for using points). Most surveys give you 10-30 points and take about 3 minutes to do. If you are "selected" for a more in depth survey, you could get up to 750 points for a single 20 minute survey. I decline to do many of the surveys, as I just don't have the time, but it's a fun way to get a bit of extra money.
eRewards offers more surveys and you rack up eRewards "dollars" which can be used to purchase rewards (but not cash). I do this mainly to get airline mileage. With $100 in eRewards currency, you can purchase 2,000 miles on a few different airlines.
Both places send emails when there are new surveys available. In addition, I do "mystery shopping" for a company that the Cheesecake Factory uses. I get a free meal there about once every 2 months.
I do this stuff mainly for fun. It's not a job with enough income, but it's a way to pass the time and get a little reward for it as well.
If you are interested in either of these, please send me a PM. I can get a bonus for referring a friend.