Save all your bookmarks online so you can access them from any computer wherever you are.
Bookmarks can be tagged for easy later retrieval.
Note that it is possible to sign up to Diigo via Facebook.
Diigo also includes the facility to easily create lists of websites which can be shared with anyone whether or not they have a Diigo account and research tools which make it possible to annotate web pages by highlighting and adding sticky notes.
It is possible to join groups on Diigo or you could create a group if you are collaborating on a project.