Technology in the classroom and teacher resources blog
Diigo - Social Tagging, Linkage and Bookmarking
Use: Social Tagging Linkage, social bookmarking sharing, discussion boards, annotations.
Description (Wikipedia): Diigo is a social bookmarking website which allows signed-up users to bookmark and tag web-pages. Additionally, it allows users to highlight any part of a webpage and attach sticky notes to specific highlights or to a whole page. These annotations can be kept private, shared with a group within Diigo or a special link forwarded to someone else.