I have been an active Criedtap member for over a few years and they have never let me down. It is completely free, no "Preminum Membership" to purchase, everyone is treated equally.
Crowdtap works with specific companies who want feedback from real people. Based on your indicated preferences there are daily questions, surveys, sample opportunities etc that are rewarded with points and the points are easily redeemed through the site and turned in to gift cards for various retailers or you can choose to donate the money to a charity.
I also like that you are told whether you are accepted for a product trial or whether they were looking for a different demographic.
Lastly, every time I have emailed their Help Center I have had an helpful, efficient response within 24 hours.