All Music Guide
http://www.allmusic.com/Comprehensive resource for all styles of music; includes reviews, biographies, discographies, and more. Now requires quick, free registration.

Classic Music Navigator
http://www.wku.edu/~smithch/music/index2.htm Music history presented in such a way as to allow the user to explore his/her own potential classical music interests using "points of familiarity."

Digital Librarian: Music
http://www.digital-librarian.com/music.html

Duke University Historic American Sheet Music: 1850-1920
http://scriptorium.duke.edu/sheetmusic A ditized collection of sheet music published in the United States between 1850 and 1920.

DW3 Classical Music Resource
http://www.lib.duke.edu/music/resources/classical_index.html  "The World's Most Comprehensive Collection of Classical Music Links." 

Folk Music: An Index to Recordings
www.ibiblio.org/folkindex/ 

Hip Hop Webliography
http://web.simmons.edu/~morrow/hiphopweb.html  From Simmons College Music Librarianship.

I Hear America Singing
http://www.loc.gov/rr/perform/ihas/  Digitized collections, including text, sould files, and sheet music, from the Music, Theater, and Dance Collections of the Library of Congress.

J.W Pepper's Resource Center
http://jwpepper.com/resources.html  Directory of music websites.

Lester S. Levy Collection of Sheet Music
http://levysheetmusic.mse.jhu.edu Focuses on popular American music, 1780-1960.

Lyrics World : Top-40 Hits of 1930-1999
http://ntl.matrix.com.br/pfilho/html/top40/index.html

Milken Archive of American Jewish Music
http://www.milkenarchive.org

The Music Division of The New York Public Library
http://www.nypl.org/research/lpa/mus/mus.html  Especially useful are the selected Internet resources and the finding aids to archival collections.

Music Lyrics Links
http://www.cannylink.com/musiclyrics.htm

WOI Radio Group's Pronouncing Dictionary of Music and Musicians
http://woi.org/dictionary