I admit it: Much as del.icio.us has intrigued me, I could never quite figure out how to use the darned thing. Lucky for me, Eric Feinblatt turned me on to a screencast on the topic by John Udell. If you're like me and you haven't quite been able to get into del.icio.us, then check out the screencast. And to get a slightly academic overview of folksonomies in general, using del.icio.us and flickr as the primary examples, you might want to read Folksonomies: Cooperative Classification and Communication Through Shared Metadata.
Once you've done so, then you'll want to look at a few more resources:The Quick Online Tips blog maintains a running list of all kinds of fun add-ons that make use of the software's API. One of my favorite at the moment is HuntandGather, a Firefox plug-in that lets me pull up most popular pages for a given tag. For example, when I enter the term "blended", HuntandGather opens up 5 web pages in new browser tabs, all of which have been taged "blended" by somebody on del.icio.us. Now, three of these pages aren't interesting to me for a variety of reasons. But tow are interesting pieces about blended learning, which is what I had in mind. One is a thoughtful, if corporate-slanted, overview of options. The other is a piece by several professors at the University of Alabama about using blended learning techniques to teach large classes. (The number of pages HuntandGather returns on a given search is an adjustable preference.)
If you aren't looking for anything in particular and just want to see what's hot at the moment, check out trendalicious. Or maybe what you really want to do is see who has bookmarked a given page and what tag(s) they have given it. If so, then you want the del.icio.us linkbacks bookmarklet. There are many, many cools toys worth playing with.
Lastly, if you want to run your own version of del.icio.us, you are finally in luck. While the creator of the site has elected to keep his source code to himself, there is now an Open Source project called Scuttle that has come pretty close to producing a complete clone. And since I believe that folksonomies are more effective when used by a more unified community of purpose (e.g., a large academic community), this is good news. It would be a great addition to, say, a university portal environment.