I believe it is! This is a bookmarking site where you can store all of your favorite sites. It is similar to the favorites button on your computer with one exception, you can see your favorites anywhere. This is particularly helpful to me since I am constantly using four computers in my life, my basement desktop, my home laptop, my school laptop, and my the computer in my coaching office. I have found that sometimes when I am working at home on my laptop and find a website I like I need to e-mail the link to myself so I can go to that site when I am at work or if I want to print it off in the basement. Not anymore! all I need to do is click on the button on the top of my screen, of course I needed to register, and it is saved to the net. Which means no more ridiculous e-mails to myself with websites on it.
I can see this being a very useful tool in a number of arenas. First as a teacher, I can bookmark some sites that I find interesting and that my students might also find interesting. I would probably have a different Delicious site for my students to see than for my personal use. The students could then read some of the web pages without me having to try to bookmark it on all of their computers.
The same is possible for sharing ideas and interesting sites with colleagues. Just bookmark it on Delicious and share it with the teachers I work with and other coaches. I can see school departments having their own Delicious site to share with each other, and also coaches sharing on different things they find on the web. Now that is Delicious.