Ipsos - My Favourite Survey Site
Ipsos is a very reliable paying survey site that sends me really regular surveys. But as well as surveys they also have things like chat forums that they invite you to and pay you for, where you discuss a video they play you for half an hour with other people, as well as free product trials and things like that. They're one of the biggest survey companies in the world and when you've got enough points for payment they're very quick to pay you.
Not to criticize as I do use Ipsos for surveys, but although their surveys are quite interesting and like you say they have user panels and discussion projects to take part in I do find they pay less than some others. It sometime takes me a while to get up to any reasonable amount worth cashing in.
One of my favorites as well, along with Globaltestmarket and Yougov
Ipsos are one of my favs too