For anyone who isn't familiar with these sites I thought I'd post a few links here. The way to get the best value when shopping online is to find the best possible price on the internet. Then when you've got the best price you can shave up to 10% or more off if the retailer participates in one of the cashback web sites such as Top Cashback, Quidco, Cashback Kings, Rpoints etc...
I've been including links to Quidco in a lot of my posts. I can confirm they do pay out via Paypal, minus a £5 per annum admin fee. Below are some of the more popular cashback web sites:
Money Saving Expert Cashback Sites Article
The cashback sites themselves sometimes offer fees for referrals to join them. Instead of just joining yourself by going to the web site, it can pay to use a friends referral link, and get another friend to use yours. That way both joiner and referrer are paid when someone new signs up.