For the past few years I have been completing the Royal Mail Survey operated by Kantar TNS Research International. The purpose is to monitor the Royal Mail postal service.
The role involves preparing letters and parcels for the survey and posting them usually with a chip called a SMART which monitors progress of the item through the postal system. You are sent a package each week which has a postal plan with the items you have to send, addresses and a schedule of when.
Whilst you post out items for the survey, at the same time you receive items posted by other survey members. You then enter details of items posted and received on a website database on a daily basis.
I find this is a good project for me and helps with my anxiety as it requires a degree of organisation, requires me to go out to a post-box or post office to post items. I gain satisfaction from completing the tasks involved and my only communication is via email and logging data on a database, I feel in control.
You are rewarded with stamps and first day covers, a diary at Christmas and mini eggs at Easter. The survey usully lasts for about 6 months. After that, I have found I am regularly asked to participate again 6 months later.
You can register, join and apply to be part of the RMS survey here (NB this is a new link updated March 2018, following TNS website update and change)