Microsoft Community Bar

Microsoft Research - Microsoft Community Bar

"The Community bar adds context-dependent content to the web browsing experience. As a user browses the web, he can see (and leave) notes from other people who visited the same page, chat with other people viewing the same page, tag the page with a bookmark or category label, view all the inlinks to the page, find related pages, perform context-specific search, and see blog postings related to the page.
 
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Sounds kind of interesting...