There are a number of free survey sites that compensate respondents for taking surveys. Some examples, as of Februrary 2015, are Swagbucks, GlobalTestMarket and e-Rewards Opinion Panel.
Some other similar sites include MySurvey, Pinecone Research and Valued Opinions.
The compensation for completing surveys at these sites is usually in the form of rewards points that can be exchanged for gift cards or for rewards points in other programs. For example, as of February 2015, e-Rewards points can be redeemed for gift cards at Best Buy or for Amtrak rewards points, among a number of other options. Direct cash payments from survey sites are extremely rare.