Pricepirates - On-the-go mobile price comparisons for Amazon, eBay and more.
Keepa - Price history charts and the option to be alerted on price drops for all Amazon sites.
PriceGrabber - Get the lowest prices on computers, electronics, furniture, cameras, clothes and more.
Shopping.com - Shopping.com is a leading price comparison site that allows you shop online for the best deals and lowest prices. You can read unbiased product reviews and compare prices online. Online shopping has never been as easy!
PepperGoods.com - PepperGoods aggregates wholesale websites to provide you with best products choosen from millions.
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.