I'm sure most people know what mystery shopping is already but just for those who don't, mystery shopping is where you get paid to try out a company's products, services or website in return for your feedback.

Emysteryshopper is a very good example of this. They have been around for many years and give you plenty of invitations. Some of their invites pay really well - I've had £50 for one before, although depending on what it is it's not likely to be as much of this most of the time. It's completely free to sign up and they pay you by cheque. They're reliable payers and you can easily earn an extra couple of hundred pounds a year from them.