This post is for websites that I either use or know of that use Mystery Shoppers. Some of the links below may be my personal referral links from the websites (I will mark these with *), but you can always go via the website direct. But most importantly, none of the websites I belong to would send a cold, blanket email asking you to join.
Market Force* is the only one out the 3 Secret Shopper websites that I actually use (it will become apparent why as you read the other two).
You complete your profile according to you personal preference, location and shopping habits and then jobs will become available based on this criteria. Unlike reviews, you will not necessarily receive emails when new jobs come up, espeically popular stores. So it is advisable to review the website on a regular basis to see if there are any secret shopper tasks which take your fancy.
You must read the assignment before accepting and check the dates by when the task needs to be completed. If you accept an assignment and then fail to complete you will get a negative score. But as you complete jobs and build your score up more assignments will become available for you.
GAPbuster was referred to me by a friend, who has a lot of experience with this company and has done a lot of secret shops for them. GAPbuster has assignments for fast food chains such as Mcdonalds and KFC, and the main reason why I haven't yet completed an assignment is due to time. Once you join, you have an orientation test to complete, and once passed you can then apply to job so of which will require another test, you will need to pass these tests before given any assignments for companies such as McDonalds.
mystery dining. I'm yet to join this site, but have it on my 'to do' list, and quite like the idea of using these assignments as part of our 'date night', as this would mean we'll actually go OUT for date night rather than saying 'lets just put a movie on'.
I hope this has helped with what sites are out there for Mystery Shoppers. If I find/use any others I'll update my page accordingly.