I like Del.icio.us a lot, actually. I've had an account with them for a while now, and I use it occasionally when I find really good links to things that I don't want to forget. It's nice to have bookmarks in your browser, but especially for someone like me who goes from computer to computer; work, to home, to my second home, and all over the place -- it's great to have a place online to store all my "stuff."
This could be particularly useful for librarians because we could keep a store of research-type links, reference links, reader's advisory links, any of the above. We all know that sometimes our toolbar bookmarks and regular bookmarks either get moved around or sometimes disappear :-x But it would be quite cool, especially with the call center upon us, to have a collaborative spot like Del.icio.us to store all of our resources so everyone can access them. Fancy.