I signed up with Clix Research a few years ago. It's a consumer research website where you fill out a number of different profiles about you and depending on your answers you become eligible for different trials.
Trials involve Clix Research sending a product out to you for free, which you then test in place of your usual product, and at the end of it you fill out an evaluation. Depending on how promptly you fill out the evaluation and how detailed it is, you become eligible for more trials.
All the products have been tested for reactions to it etc. your job is just to test how effective you think it is in comparison to your usual product, how you'd describe it and so on. It's a really good way to get to try out some new things...
The down side is this, you have to keep the details of the trial a secret, the product is nearly always sent to you in unbranded packaging, Clix Research more often than not can't tell you what the product you're trialling is AND not all of them even end up on the market! For example a couple of years ago I was sent an amazing face cleanser especially formulated to get rid of blackheads. It worked wonderfully and I loved it, but when I emailed Clix Research to ask them if they could tell me what it was I discovered they weren't allowed to tell me... NOOOOO!
In my opinion this is something worth trying out, you get something new for free that you may well love, and in turn you evaluate it. You need to be 18 or over to sign up (although I wasn't at the time...!) although you can add family members' profiles who aren't (for example, a baby) it's just when you sign in to check for trials you need to put in an age that is over 18. Confusion!
Thought this was something that was worth sharing, hope someone benefits from it!