CTI music: Information on how to join numerous music related lists run by enthusiasts or professionals.
Directory of Musical Email Lists: Information on how to join lists about musical genres, instruments, organizations and theory.
Plastic the List: A list of mailing lists dedicated to the discussion of women in rock/girl bands.
The Supersonic Guide - Mailing Lists: An index of artist-specific mailing lists
The Wharehouse: Open trading lists for many pop styles; also includes font list, graphics list, mp3 list.