Quidco.com

Get paid for shopping

Over the last few years I have earned nearly £1500 cash back from Quidco. All on things that I was going to buy anyway.
The trick is, to find the best deal for what you want to buy first, then see if that company is offering some cash back on Quidco. That way even if the cash back is declined (Which hardly ever happens) you still brought the item for the best price.