It's not a lot of cash, but an extra £50 every few months for doing surveys and making your opinion count a little.
They don't spam you, you get 50p for each survey you do, and you get a pound just for joining, some times double points are available and you can enter the weekly prize survey where you are entered into a draw that could win you between £25 - £250. They only send you the money when you have £50 in your account which is a nice amount to go out for a free evening with and the surveys take from 2mins to 10mins.
Click this link to join, it's worth it. The money is slowly building up in my account and a lot of my friends are at the £50 mark already!
YouGov plc - Understanding People