I've heard about this site before but never did set up an account, and even now I'm not sure I'd really use it. I find all the tags and comments to be confusing and overwhelming, and not all that helpful. Possibly I would use it for my own bookmarks, but I've got Foxmarks installed so things automatically get synchronized between my PC and laptop. I do see how the Reference staff could use this to share favorite sites between all staff, especially for those who work at several different desks and computers in our library.
I did find some new and interesting sites: the Penguin books podcast and Juice, an open-source podcast receiver.
I think the Penguin book idea is great - libraries could create similar podcasts with staff discussing new titles (but there is that pesky staff time issue to deal with!) I think I'll subscribe to this - I do have an online book club subscription that arrives daily in my email, but that requires actually reading the chapter! It would be much more convenient to listen to a podcast. This isn't exactly the same: it's not just a chapter, there seems to be discussion too, and it's not daily (these do take time to produce!) but there is a lot of potential here.
I'm wishing I'd found the Juice site earlier, before I installed iTunes on my home computer, just because I like open-source as a matter of principle. I've gotten other software from SourceForge (they have a great PDF creator!).