I earn extra income doing consumer surveys and product trials on a GPT or "get paid to" site.  Unfortunately there are some scams out there so you should always steer clear of any home business site that charges you to join or has no forum allowing you to interact with other members.  You can tell that my favorite site is legitimate because it is free to join and you can hear feedback from other members on the site's forum and chatroom. 

Companies will pay you for trying out their products and surveys / getting some honest feedback.  They do this because they're hoping to get some new customers.   There are hundreds of offers to choose from and the site is totally free to join.  Whenever you earn at least $20, the site will send you a check in the mail the following month. 

There are two basic types of offers;  surveys & trials:

You can earn money doing surveys (aka 100% free) offers.  These don't pay as well as the trials but there no credit card will ever be required.  Sometimes you can get paid simply for signing up to another site (i.e., MyPoints).  Some surveys will ask for your name, address, phone # etc.  If you do any of these I recommend getting some free email account/s and a free voice mail # from privatephone.com so that you will not get unwanted SPAM or telemarketing calls.  The cash surveys work best when you clear cookies in your web browser before doing another one and limiting yourself to 5-7 surveys per day. 

Trials tend to pay well ($10 or more) and involve actually trying out a product or online service.  Some trials require a credit card because the company will charge you regular membership fees if you decide to keep the service past the trial period.  Many trials are totally free- a few trials will charge small shipping / processing fees up front, although you will get that money back, and then some.  If you do credit card offers, you may feel more comfortable using a prepaid credit card or Visa giftcard.   However, most of the companies that advertise on GPT sites are pretty well known and can be considered very trustworthy companies to deal with.

The site's forum is very informative and a lot of contests (with prizes) are featured there. I've personally made over $1600 from doing this in my free time for a few months. It's not a full-time gig, but a great way to make extra income if you don't have time to get another job. This site is great for stay at home parents and college students.   For more info: http://nodavesclub.blogspot.com/