LoveSales - Find and save products you love, get alerted when they go on sale.
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
Thinkover - Drag and drop and make collections out of images and links on websites.
Fetchee - Fetchee is a free price tracking wish list app that works with all online stores worldwide.
TrackIf - Alerts you if the price of your favorite products drop
Keepa - Price history charts and the option to be alerted on price drops for all Amazon sites.