This little site is an international Amazon stores comparison engine.
Amazon has 6 stores in the world: USA, UK, Germany, France, Canada and Japan. A lot of products are offered in all the stores, or many of them. Well, prices vary A LOT between stores. If you are from the US, you can get cheaper products from Canada (music, dvs) or UK (import music mainly). If you are from somewhere else, it’s even better! People tend to think that the best store to order from is the nearest one. Well, that’s absolutely false. Europeans can usually get stuff cheaper from the US (including shipping) than from any other European store. And for other countries, this site shows you many Amazon stores to check and it sure can have nice surprises.
The site gets prices, puts them in your currency and then adds shipping cost to your country (looks like they get it from your IP).
Pricenoia has a couple of nice add-ons. A bookmarklet that lets you compare prices when you are looking at a product page at Amazon, and a graph of the price evolution over time for every product in every store.
A great tool for the holiday season, and a good reference for the rest of the year!