I have been a member of Synovate for over a year now and enjoy the variety of surveys I receive from them. Also, they frequently send me items for product tests and I love product tests! Synovate emails are from the name "Marie Brighton" and I average about 5 per week. I qualify for the majority of them and their threshhold of $10 to cash out is reasonable.
It's FREE to sign up for Synovate. Use your separate email address for surveys when you sign up. I don't get any spam from them but it's easier to have all your survey invitations in one inbox apart from your personal emails.
For more information on other survey companies I am signed up with, check out my previous survey posts.