The Chopin Files
Chopin Nocturnes, Etudes, Waltzes, and Preludes in PDF, MIDI, and realAudio

GMD
Music Archive of classical works in several formats.

Faber & Faber
Publishing Resource for Piano Teachers and Students.

Jeffry Hamilton Steele
Classical Guitar CDs, audio downloads, sheet music ranging from solo guitar to large-scale modern dance productions.

Saraband Music
Early music specialist in Australia. Medieval, Renaissance and Baroque sheet music and facsimiles...

ComposerMusic
Several dozen works, mostly for piano, in PDF and Scorch format.

Free Sheetmusic from Johan Tufvesson
Mostly from the 17th and 18th centuries, and concentrating on Scandinavian work. (at Project Runeberg)

Romanian Scores Library
Free scores of Romanian classical music by Bartok, Enescu, Dumitrescu, Avram and others.

Classical Guitar Archives Music
Musical and technical information: sheet music, MIDI, freeware, resources, realAudio clips, and events.

Eerland.Net
Cesar Franck's l'Organiste, in PDF and MIDI format.

Free Music for Brass Ensemble
INcludes arrangements for Symphonic Brass Quintet and Brass Band Quintet, PDF format.

Guitar School, The
Many pages of free pieces for classical guitar students.

Music Scores
Includes PDF-format scores, some with arrangements for various abilities and instruments.

Hebe
Downloadable music, including the New Complete Works of Sor.

GMD - Music Archive: Sheet Music
Classical sheet music in MusiXTeX, PDF and PS formats.

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

Latham Music
Ensembles for students and professionals.