Pricepirates is a free shopping assistant for your Mac. The app lets you check prices of items on eBay, Amazon and Shopping.com.
It supports storefronts for a few different countries: United States, Germany, Austria, Switzerland and United Kingdom. When you carry out a search, the application will display all the results for the three sites in a single window, separated in tabs, with clear information about each result. For example, I carried out a search for the Apple Magic Trackpad. The first results that I saw were the ones from Amazon. I got 9 results in Amazon, and only one of them was the product I was looking for. eBay was another story, I got tons of results, and most of them were accurate. For each item that was found, the application showed a price, shipping price and used price for Amazon and Buy Now and Auction prices for eBay. This made calculate prices and see what the best offer was.
The one feature that I really like about this app is its watchlist. As you may know, you can have watchlists on both eBay and Amazon, but with this app, you can add products from both websites to a single list and compare them side by side.
In conclusion, if you regularly buy on either Amazon or eBay and often compare prices between those sites, this app can be very useful.