Foogle's Google's excellent shopping search engine. Of course you can always just use the shopping tab option on Google searches.
Shopping Robot - helps you find the cheapest prices and stockists of the item you want.
Compare prices and products before you shop. Pricerunner shows competing suppliers' prices for any given product.
Quidco is a good Cashback website, where you can earn £’s shopping at over 4,000 major retailers such as; Tesco, Debenhams, Marks and Spencer, HMV, Sky, O2, ASDA, British Gas, Lastminute.com, B&Q, and many insurance companies and mobile phone operators.