I registered with YouGov a month or so ago, thinking that perhaps I'd earn 50p for a survey and have done with it. But now I see that my account currently stands thus:
Bonus Credit (including Joining Credit)
... which means I am nearly 1/4 of the way to receiving a cheque for £50.
It is well easy to join up too, you just click this 'ere link and it lets you set up an account straight away. And if you refer a few of your mates you'll get extra credit for referring them!
Free money! It's like a dream I had once...