Via Peter Reiser's blog a pointer to this very cool experimental mashup using Wikipedia, Open Calais, Goggle and Amazon that demonstrates how to use semantic based term extraction and the Amazon API to search for relevant books for a specific topic like for example i used Dow Jones which brought back books on the Wall Street Journal which is one of the Dow Jones properties.
From Peter's Blog: How it works
1. The search input is sent to wikipedia.org
2. The respective wikipedia page is sent to the Open Calais service to extract the terms
3. The extracted terms are sent to google, and get enriched by related terms using the google labs service "google suggest".
4. the terms are sent to the Amazon API and the relevant books from Amazon are displayed
A simple use case for this could be a blog widget that would semantically extracted information from posts, like for example on this post an Amazon widget would present books on the Semantic Web, Google and APIs with my affiliate ID embedded so if a reader wanted to purchase books related to the subject of the specific post they could.