Domcomp - No-nonsense domain price comparisons, updated daily
Waatcher - Automatically buy on Amazon at your target price
Music Flee - Compare prices of music from iTunes and Amazon easily.
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
Pricepeek - Compare prices of the same product across all Amazon locales
Inside Deals - Hand-picked products, deals, and ways to save money.