lol, well it doesn't work as well for everyone. I've given them to some friends after showing my Amazon vouchers list and they don't get many. (i've received over £1500 in vouchers since mid 2009..and >£500 cash). Sometimes it dries up a bit, other times i get flooded with them and can't keep up.
You may only get offered £1 for a 20-30 minute survey. Not a lot, but the trick is that once you've done a lot you get used to the layout and now that 20-30 minute survey takes me about 10-15 minutes.
Also, you have to be willing to give out personal details. Although to be honest, for 2 years i've had no increase in junk mail from doing so.
I'm registered with many sites. (if you want you can PM e-mail address and i can send a referal - then i get a little extra too!)
newvistalive
globaltestmarket
valued opinions
panel base
toluna
ipsos interactive
gfk
harris poll
mindmover
Those are the main earners for me.
You don't get much, so i'd never do this at home. But if you can do them at work then it's a nice little earner to be honest once you get going. It can take a while to get going because you won't hit your first payout for a few months. But once you get to that point you have payouts coming in regularly.
Not all pay in amazon vouchers, some pay cash. You may also win prize draws too. I won £100 once and many £5 and £2 vouchers.
The beginning is the worst as you'd have to create a profile with each site. But it really can be a nice bit of extra money to fund a hobby such as gaming.
Oh, and Topcashback works too and is legit. Buy things online from TCB site and get often 5-10% back! Again, it's nowt amazing but it makes most things you ever buy cheaper. You can even get paid to sign up to these survey sites above (some of them) and also sign up to free trials. (especially lovefilm).
http://www.topcashback.co.uk/ref/blitzwing85