Social bookmarking...I tried explaining this to my husband and he thought it was an alternative to facebook or mspace. I then took him on a tour of his bookmarks saved on our computer. He is also a graduate student and he has an entire folder that is dedicated to his grad work. In fact I have had to email him websites and articles to his email address that he accesses from other parts of the country. So I was introduced to Diigo. Very similar to delicious. I like Diigo because of the ability to share with my groups that I have set up, I can post post-it notes to websites so I know why I bookmarked it, and I can create my own Diigo dealing with specific topics. That is similar to delicious. My favorite thing about Diigo is the post-it note.
Regarding delicious, it offers the similar features as Diigo, that is the social sharing of bookmarks, group creation, and the catagories. I like delicious format and it was very easy to navigate around. I think any of the social bookmark sites are great for the main purpose of having the access to your bookmarks. I did sign up for the RSS feed because I think that some the articles I saw listed and the entire theme of the group is great for my professional development.
I started this year with my seniors who are working on their senior research project from the beginning of the year, with an introduction of Diigo. I did not force them but some saw the value in the service and created their accounts.