Over the years of having multiple campuses I have simply saved websites to the network at school so I could access them on my different campuses. I became familiar with Delicious a couple of years ago. This last school year I really took a look at this site and realized how helpful this could be to me and also save huge amounts of time. With three campuses last year I didn't even have time to "play" with this site. I am planning on moving everything over to Delicious here in the next few weeks.
I can see where having an account for students / schools to use would be helpful for research or lessons. This is a great way to organize that would save time for me as a librarian, but also for students and teachers! Tagging reminds me of a card catalog for websites!
When I went to Magnolia it was under construction and I couldn't play with it. The Furl came up diigo and that was interesting. However other than Delicious I found Digg to be the most user friendly and the easiest to use. Digg is a tagging site that I can see recommending and sharing with professionals and students.