Just signed up for this as recommended by a colleague. Looks like they run a lot of postal surveys for Royal Mail etc. All related to sending and receiving mail and entering a few pieces of information on their website. You just have to be lucky enough to live in an area where they measure the post and willing to check your mail everyday.

You get stamps or vouchers depending on the survey you participate and they also do a lot of prize draws. Did a bit of googling and they seem to be legitimate and actually pretty good - so why not.