When I first began to read blogs, there were lots of really good ones about libraries, but not too many about cataloging specifically.
Now there are several and more are being created. A new one is Cataloging Thoughts based on the personal experience of Steve Denney, a library assistant at the University of California, Berkeley.
I haven't had a chance to read any of his posts, but I've added the title to my blog reader and also to the list of blogs on the Catalogers pages of the CMRLS website.
I learned about this blog through the electronic discussion list RADCAT. Blogs and discussion lists are a major way for me to keep up with what's happening in the ever changing field of cataloging.