or those who do not know, Diigo, according to Wikipedia, is:
Diigo (pronounced /ˈdiːɡoʊ/) is a social bookmarkingwebsite 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. The name “Diigo” is an abbreviation for “Digest of Internet Information, Groups and Other stuff.”