An excellent and very comprehensive collection of articles from Wikipedia, the free on-line encyclopedia.
The American Musicological Society's mission is to advance research in the various fields of music as a branch of learning and scholarship.
IMS' purpose is the advancement of musicological research on the basis of international co-operation.
The American Music Center is dedicated to building a national community of artists, organizations, and audiences creating, performing, and enjoying new American music.
Musical America today is the meeting place for the entire performing arts industry.
artsJournal, the daily digest of arts, culture and ideas, has this page devoted to music.
Music For the Love of It is a bimonthly newsletter for people (and others) who love making music. It is a musically literate forum in which amateur and professional musicians share stimulating ideas, up-to-date technical information and heartfelt enthusiasm for music-making.
Dolmetsch Online's guide to music theory.
A large and very active message board for discussing all aspects of music.
A free service which aims to support musicians in every aspect of education and performance.
"Ideas and resources for great music lessons."
Google News: Music
Google Scholar: Music
Google Books: Music
Yahoo! Directory: Music