amapedia home page
Brilliant idea by Amazon.
They've setup their own version of Wikipedia that seems to revolve around the products within their site. They've cunningly put it on a fully separate domain from their shops.
The trick is that they now get two listings within Google. One for their shop and one for their 'nice' site explaining all about the book but not in a "selly" way.
Of course it has nice convenient links for you to go and buy it on Amazon no matter what you write in the copy.
It'll be interesting to see if any companies copy it. It'll be difficult to get the critical mass to push some content into it, but getting two places on the top page in Google is definitely worth it.