Del.iciou.us is an awesome site. I love being able to find something specific and just tag it, without having to worry about which folder to place it in my favorites (which now has so many pages, that it's hard to keep up with it all). This site manages all the pages that I found interesting, and then I can go and categorize it however I feel. I often find myself stuck to my home computer, mainly because of all the sites that I have saved to my favorites....Well those days are soon going to be gone, thanks to this.
By searching around through other peoples tags, I found was a very cool feature. It's like being able to search through someone's personal computer and find exactly what they like. This really brings in those hard to find sites to a much wider audience.
As far as instruction wise goes, I think this can be a great researching aid. Google and Yahoo, can only do so much, but when you start seaching through tags, and specific tags, then you'll find exactly what you're looking for.