In the April 18, 2005, issue of Newsweek, "The Technologist" column is about "tagging," sites like Flickr and del.icio.us, that collect users labels for things. These "things" can be absolutely anything - the great thing about the Internet is that communities can appear almost instantaneously around anything at all. These labels can then be used to generate a folksonomy. There's a lot of buzz out there about folksonomies right now on the Web, and it's well-deserved. It's cool stuff. It provides such a great sense of how REAL PEOPLE (who?) think about things.
I'm enough of a skeptic to think it's not practical for libraries to switch wholesale to folksonomy-type endeavors for subject access, but surely there are ways in which we can capitalize on the wealth of relevant information being generated out there. I've been interested for some time in incorporating user-contributed to a project I work on. My plugs for this to date have used Wikis as examples - I think I'm going to have to add folksonomies to my spiel!