Keepa - Price history charts and the option to be alerted on price drops for all Amazon sites.
LoveSales - Find and save products you love, get alerted when they go on sale.
PriceGrabber - Get the lowest prices on computers, electronics, furniture, cameras, clothes and more.
TrackIf - Alerts you if the price of your favorite products drop
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!
Giftwhale - Giftwhale allows you to create personalised wish lists online.