Groups part of the name. In addition to having awesome annotation tools, it also has a lot of great ways to share information with others, formal and informal. First you can send bookmarks not just to other Diigo members you’re “friends” with (sort of like the for:username feature in del.icio.us), but also to emails (I use it to send stuff to my spouse who refuses to join a social bookmarking site), and to your existing del.ico.us account. That’s the easy stuff. You can also form more formal groups within Diigo. You can share bookmarks (with your notes) to a group, and it will appear in the groups bookmarks.
It doesn’t stop there though. There’s a full discussion forum feature, so you can have a discussion where you invite other individual Diigo members to discuss a bookmark or just ideas for that matter, or you can have a discussion within a Group you belong to. Think of how you could use that with students to facilitate discussions around online reading. It takes the social part of social bookmarking to the next level. Some teachers have even used this feature to form study groups for students.
