Information about copyright law and free sheet music
http://www.publicdomainsherpa.com/public-domain-sheet-music.html

Vast resource of Free downloadable sheet music- ‘Sharing the world’s public domain music’.
IMSLP stands for International Music Score Library Project. It has over 90,000 scores
The Petrucci Music Library IMSLP.   http://imslp.org/wiki/Category:Composers

From Terence Charlston, one of the UK’s leading early keyboard players
A small number of keyboard pieces available as PDF files for free download
http://homepage.ntlworld.com/terence.charlston/

Jacques Duphly; Pièces de Clavecin, Books 1, 2, 3 and 4 downloadable in modern notation,
together with information about the music & the composer.  http://jacques.duphly.free.fr/­

Antonio Soler- downloadable sheet music of 120 Keyboard Sonatas,  the Fandango and 4
Concertos for 2 keyboards.   http://www.chateaugris.com/Soler/audio-music.htm

The Mutopia Project: Free sheet music for everyone. Music is supplied as PDF files for easy printing on either A4 or US Letter paper. The LilyPond source files are also available. http://www.mutopiaproject.org/