"One great tool for creating social reading experiences is Diigo (www.diigo.com), a free online application that allows users to add highlights and comments onscreen to any Web-based text. These comments can be seen by anyone using Diigo and are identified with the commenter's user name. Diigo also enables users to bookmark and "tag" with keywords any online articles that they find fascinating."
Pearltrees now allows you to organize collections of links, videos, images, and files. All of your collections appear in your Pearltrees homescreen and from there you can access and add to any of your collections