Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
Fetchee - Fetchee is a free price tracking wish list app that works with all online stores worldwide.
Paribus - Find out for free if online stores owe you a refund!
LoveSales - Find and save products you love, get alerted when they go on sale.
Savelist - Found products you want but not ready to buy?
PriceSpy - PriceSpy helps you save money when shopping online.