Surveys and Focus Groups
You can earn money or free items by completing surveys online, but many sites aren't legitimate and will not pay out as agreed. Here are some places that you can trust.
Survey Police: Survey Police provides rankings of satisfaction for nearly all paid/reward survey companies on the Web. Before you sign up, you should check their site to see if the survey company fulfills its promises of payment.
SurveySavvy: SurveySavvy offers payment for each of their surveys. Most surveys are around $2 (the minimum), but some can pay $35 or more if you qualify. You can cash out at $2 as well, so you can be paid after doing your first survey!
BzzAgent: BzzAgent is a different kind of survey site. BzzAgent allows you to try new products free of charge (they even cover shipping) in order to get word-of-mouth advertising. They're usable products worth getting, too - like a box of Atkins bars or a Sonicare toothbrush. BzzAgent also manages to be a lot of fun! You won't be paid for surveys, but you can earn points to redeem for BzzAgent swag, charity donations, and more.
Google User Experience Research: Google offers pay (typically $75 per hour, but varies) for surveys and focus groups related to its products. Sign up on their website and you can be notified if selected for one of these studies.