Greenfield Online is a large survey company with lots of surveys for you to take. Many Greenfield surveys get you only an entry into their sweepstakes while others earn you cash. You need a minimum of $5 to cash out and they will mail you a check within a few weeks.
I have been signed up with Greenfield for 6 months now and have cashed out several times. I have also been invited (and qualified) to participate in several online bulletin board/forums that earned me $25! Greenfield will send daily invites but I ignore the ones that aren't for money unless I have some time to take them. Sign up for FREE with Greenfield online here.
If you consider yourself Hispanic, Greenfield has a special panel for Hispanics that you can also sign up for FREE at right here.
Some of the other surveys companies already reviewed on this blog are Global Test Market, Survey Savvy, SayNation, Valued Opinions, American Consumer Opinion, Opinion Outpost , Zoompanel, Ipsos I-Say, HCD Surveys, and university-sponsored sites. Have you signed up for all of them?