Best Price Comparison sites

Price comparison sites can collect data directly from merchants. Retailers who want to list their products on the website then supply their own lists of products and prices, and these are matched against the original database. This is done by a mixture of information extraction, fuzzy logic and human labour.
Comparison sites can also collect data through a data feed file. Merchants provide information electronically in a set format. This data is then imported by the comparison website. Some third party businesses are providing consolidation of data feeds so that comparison sites do not have to import from many different merchants. Affiliate networks such as LinkShare, Commission Junction, Affiliate Window & TradeDoubler aggregate data feeds from many merchants and provide them to the price comparison sites. This enables price comparison sites to monetize the products contained in the feeds by earning commissions on click through traffic

Best Price comparison sites
Site Info
Pricegrabber offers the best online shopping experience. The unique shopping site offers extensive inventory at the lowest prices by comparing products, product reviews, and merchant deals for all of your shopping needs. Browse thousands of popular brands, hot products, featured deals and find exactly what you want at discount prices is a leading price comparison site allows buyers to shop best deals and lowest price. shoppers options are more including ebay products . partner site
Yahoo! Shopping offers all kinds of products price comparison by getting the price information from maximum number of online sellers
Nextag fetchs millions of products to buy the best one for the users .This site also maintains the price history for the products.
Shopzilla provide good user interface to compare the different prices of the online sellers.
Mysmartprice allows to compare prices of products like Mobile Phones, Books and Cameras, available across various popular online shopping websites like FlipKart, Infibeam, HomeShop18 etc. in India.
alatest The website alaTest is a review aggregator launched in Sweden.It currently aggregates and analyzes 11 million reviews from over 1800 websites. It also provides reviews for major sites like Microsoft Bing (search engine), eBay, Samsung Electronics, Philips, Nikon, Sony Ericsson, Nokia, ZDNet and several price comparison web sites.
Books Store Info
abebooks AbeBooks' users can search across the listings of many independent bookstores, thereby allowing small, independent players to compete with bookselling superstores. Some of the member bookstores offer their books online only, while others also maintain a regular storefront.