Fanastic idea: Primarily using Amazon.com's Web Services API,
Amazon Light 4.0 is an exercise in tying together various Web Services into a whole, adding content, context and some useful tools to the Amazon shopping/browsing experience.
A number of existing popular and/or useful web tools were tied together into the site itself - Yahoo News for relevant news stories, Google Search for relevant sites, One-click offshoots to GMail, Netflix, iTunes, Blogger, Dropcash, Del.icio.us, Local Libraries and a couple more things.