Development & Missions Network
This is brilliant. It checks your area for the broadband services available and then allows you to compare the prices and services of the providers.
Google's very good shopping search engine.
Shopping Robot - helps you find the cheapest prices and stockists of the item you want.
Check prices of just about everything - from general shopping to utilities to travel, banking, insurance and more.
Compare supermarket prices and shop online - find the best possible price for your groceries.