You can discuss almost anything on the web or via email. And that includes library stuff. Most listservs offer archives of their postings so you can get an idea of what they talk about and how active the list is before you subscribe. In addition, several lists provide annotations of new and interesting websites for educators.
Listservs:
The Acquisitions Librarians Electronic Network
The American Library Association offers several different lists:
Classroom Connect: a variety of lists that deliver annotated websites to your inbox
Blue Web'n: sends out an email with five new websites each week