John Krystynak recently released his newest creation, Aytozon.com . By using the APIs provided by Amazon and eBay, Aytozon performs parallel searches on both sites, unifies the results, and presents them in side by side fashion for comparison.
The search results are quite interesting. The screen shot at right (click for a larger view) shows the results of a search for the string "Porsche 911". The first page of results for the eBay search includes car parts and a book or two. The corresponding page of Amazon results includes a few parts, some books, and some non-automotive products from Porsche Design.