Well, I've learned about del.icio.us, but I haven't gotten too excited about it. When I checked out the libraries that are using it, I felt that its overwhelming. Too many sites to look at. Guess I'm an organized/limited time person and like to "cut to the chase." I want a short list of links not a long list of topics to scroll through. Guess I'm in the minority. I'll have to use it more often to see if my opinion changes.
I do like the concept of tagging. Somebody may assign a better tag to a book than I would or have a different perspective on a book than another person. Again, I'll have to get used to putting tags on my blog and also the library's Hot Topics page.