Paribus - Find out for free if online stores owe you a refund!
Lolli - Earn bitcoin when you shop online
Gruupz - Get money back on every purchase you make on Amazon.
Earny.co - Win prizes on Amazon purchases
PriceSpy - PriceSpy helps you save money when shopping online.
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.