Diigo.com is a social network site and more. You must create a Free account to start this. Once you create the account Diigo will send you an verification e-mail. Mine was delivered to my junk mail. Being a social network site you can then create your own dashboard (website) with information related to you.
Let me highlight a few things it can do.
1. It’s a bookmark site. By that I mean you add and organize your book marks similar to your browser. As you create the bookmark you add tags (terms that describe the site making it easier to sort).
2. You can share your book marks with others with similar interest. For example right here at HHS all the science teachers could share the bookmarks of sites they use or find related to the field of science. Think of the power. Instead of searching alone on the Internet you become a department system. Better yet, you can find others on diigo that have similar interest and join their book marks. This opens you up to thousands, thousands and thousands of possible sites.
3. You also download a tool that becomes part of your bowser. (This is easy to do and only needs to be done once.) When you find a site of interest you click this tool. Now you can highlight parts of that website. Then when you visit the site again it remembers what you highlighted!
*Tool 
Photo by http://farm4.static.flickr.com/3043/2622997333_034e0fb9f3.jpg
Sticky Notes
Photo https://peteandcentral.wikispaces.com/file/view/Picture_3.png
4. Another use of the tool allows you to create sticky notes (notes that float on top of the site). You can add comments that are private or shared with any groups that you belong to. Like the highlight it remembers your sticky notes as well when you return to the site.
Photo by http://www.online-tech-tips.com/wp-content/uploads/2008/04/highlight-and-add-comments-on-diigo.jpg
(Note: to see anything you highlighted or a sticky note you must click on the Diigo button that was installed. This is what helps it remember all that neat stuff.)
5. Another use of the tool allows you to make comments but to me this is similar to sticky notes.
6. As #4 stated. You can join groups. These groups are others on diigo that have similar interest. So not only can you share your sites but you can share your comments with them as well.
7. Find out who else is looking at a web page.
Photo by http://www.online-tech-tips.com/wp-content/uploads/2008/04/diigo-users-reading-the-same-content-1.jpg
There’s so much more. You can learn more about Diigo.com by visiting YouTube. This is a 9 minute video that highlights how this all works. http://www.youtube.com/watch?v=kcecBgRd3ig
