[This is still very much alive as at January 2014. Now actively recruiting. They have a policy of 'resting' people for a few months after a while, and as people are 'rested' they bring in new people.]
Basically, you have to post a few letters (around 5 or 6) every week for them, and log a few letters received (again, around 5 or 6 a week) onto their online system.
In return, you get 12 First Class and 4 Large First Class stamps every month (worth £8.52), occasional bonus stamps or gifts, a yearly diary and occasional prize draw wins if you have average luck (there are 14 daily prizes of £10, and a monthly £750 prize).
Easy money for the small amount of work involved.
More here: http://forums.moneysavingexpert.com/showthread.php?t=3872901&page=98
How Quick is Royal Mail?
10,000 people at addresses all over the UK participate in the official independent measurement of Royal Mail’s service.
TNS Research International is commissioned by Royal Mail to deliver this project.
We’re always looking for more people to take part by representing their own postcode area.
To find out if you’re eligible and receive more information about the project (including the incentives that we offer) please complete this short questionnaire.
Sign up through the link provided, and in after a few days you should receive this email:
There is an opportunity for you to represent your area on the Royal Mail Survey.
This project measures Royal Mail's service and helps them to identify specific parts of their network that require improvement. About 6,000 panellists participating from business and residential addresses post items to each other. TNS Research International calculates how long it takes for Royal Mail to deliver those items.
We'd like to invite you to join our panel of 6,000 panellists for a fixed period of 6 months during which we'll ask you to send and receive a variety of letters. In exchange, we will send you a monthly incentive of 12 x 1st Class stamps and 4 x 1st Class Large Letter stamps, 2 sets of Presentation Stamps, and entry into a prize draw to win High Street vouchers.
Even if you are not available at this point in time, we'd be grateful if you would let us know either way by clicking on the following link:
Royal Mail Project Team