Until now I've never had any reason to use del.icio.us because, mistakenly, I started out on mgsOnline as an HTML-based traditional website. I wish I had used del.icio.us for some of the teacher research section now. The Guardian have been using their version for some time. The Folksonomic Zeitgeist to shows readers the hottest topics of the day. As soon as the code is made available I would love to see it added to school websites and blogs.
I've created my own selection of links to things I have been reading recently, and blogs I subscribe to. The 'cloud' of tags to the right are the words I have given to each link to describe what each is about. This allows me to group like-minded links together in a limitless number of combinations. It allows you to see which type of article or site is most popular with lil' ol' me.
And in the classroom...
This type of 'tagging' could be used in the classroom environment in quite an exciting way. Each class has a del.icio.us page with links to other classrooms' pages, too. As new homework is given on a particular subject, or external links are suggested both students and teachers assign these links with tags to the del.icio.us site.