Nocturnes.com

Variations: Online Music Scores
Experimental (but large) archive of online (not printable) sheet music, some synchronized with audio recordings.
www.dlib.indiana.edu/

GMD - Music Archive: Sheet Music
Classical sheet music in MusiXTeX, PDF and PS formats.
icking-music-archive.sunsite.dk/

Kay's Secondhand Books & Used Sheet Music
Music offered includes choral, classical, electronic, general and oldies.
www.kaysmusic.com/

Sheet Music Online's Choral Music Index
Offers a by-composer categorized listing of PDF sheets.
www.sheetmusiconline.net/

Sheet Music Online
Large catalog of classical and popular music, instrumental or vocal.
www.sheetmusic1.com/

Classical Guitar Sheet Music Scores Download
Adobe Acrobat-formatted scores with corresponding RealAudio: 23 original compositions, 5 transcriptions; by Richard Miles Jackman.
www.classical-guitar.net/

Cherubic Hymn of the Georgian Church
Features an unusual harmonized chant from an Eastern Orthodox communion.
www.angelfire.com/

Vocal Chords Sheet Music
Downloadable piano accompaniments for singers and pianists, transposed into multiple keys. Includes three free samples, catalogue, and tips.
www.vocalchords.com/

Sheet Music
Free choral sheet music from the University of Alicante.
www.geocities.com/

About.com Antiques: Sheet Music
Article on collecting old sheet music.
antiques.about.com/