Brief and interesting post @ RSS4Lib about projects to tag various library catalogs, and the relevance of lesser used tags. No mention of PennTags, but there is a brief mention of MTags from the University of Michigan.

The real value of tagging is like that of a library: it's the collections, the constructed universe of things that someone (a librarian, a subject expert, a user) brought together.

Library of Congress announced today that it has partnered with flickr, putting up 3,000 photos from two of their most popular collections.Only images for which no copyright restrictions are known to exist are included.The LOC blog post about it is here:http://www.loc.gov/blog/?p=233The flickr page is here:http://www.flickr.com/photos/library_of_congress/

Although the introduction of this article is overly simplified in terms of the changes in library technology (I couldn't help but laugh a little in a couple of places) , once you're past that, the rest is a good little overview of some of the more popular opensource products.