Clickriver appears to be AdWords for Amazon -- web ads placed on Amazon.com -- and a first step toward an AdSense competitor. From the Clickriver About page:
Clickriver Ads is an advertising program ... that allows businesses to place sponsored links on Amazon.com.Back in April, in a post called, "What will become of A9?", I said:
Clickriver Ads will appear on Amazon.com, on search results pages and on many product detail pages.
With Clickriver, a wide range of complementary products and services can be advertised at the precise moment that someone is interested -- as they shop, browse, and search on Amazon.com. For example, ads from banks can display on pages for finance and investment books, such as on the "Road to Wealth" product page. Ads from photo printing services can display next to search results for cameras and tripods. Ads for hotels, car rentals and travel agencies can display on pages for travel books, sunglasses, suitcases, portable DVD players and other travel accessories sold on Amazon.com.
Clickriver Ads was built by A9.com, a search technologies company based in Palo Alto, California. A9.com is a wholly owned subsidiary of Amazon.com.
A9 could switch to focusing on AdWords and AdSense-like advertising, building on the success of Amazon Associates.Looks like that is exactly what A9 is doing.
A9 would compete with Google not on web search, where Google has a strong advantage, but on advertising, where Amazon has its massive catalog and experience selling products to leverage.
[Found via Gary Price, John Battelle, and John Cook]
Update: Om Malik says, "Amazon doesn't really want to be a retailer some days, does it?"