I have heard of del.iciou.us before, but hadn't had a chance to check it out. I had a great time! I really like the concept of being able to access my bookmarks from any computer (it's sooo frustrating knowing I have a site bookmarked at home but have to do detective work to find it from work, or vice versa). I also really like the use of tags (or, to me, keywords) that lets you find a bookmark multiple ways instead of the traditional hierarchical arrangement that limits each bookmark to one spot. It's like finding a book with keywords.
I definitely want to try to transition to using del.icio.us as an alternative to my regular bookmarks. I even saw that you can import bookmarks from your browser. The only problem with that is that I have so many old bookmarks - I would want to do a good edit/delete before I just imported everything to del.icio.us. (Another project! :) ) I also want to try using a set of del.icio.us tags for research project recommendations. I have a school library website where I add pages with links for class research projects, but I think using del.icio.us could enhance that, so I am definitely going to give it a try in the fall.
One of the libraries that use del.icio.us tags I checked out and really liked was the San Mateo Public Library. They have prefixed each tag with the high level Dewey classification, then grouped the tags under the classification number. So, you can look at the list of tags on the right side of the screen by Dewey classification category. Very cool.