These are some sites I use for general classical sheet music (not specifically classical guitar). I like to use these for music analysis. They are not for my instrument but I liek to go through the great classical masterpieces and analyze how they were composed. I find that musical analysis is the best way to learn to write your own music... it is the real secret, and for some its obvious but there is a time in every musicians career where you aren't sure how to learn how to write good music. Before one can effectively analyze other music, you need to know your theory. Just some info I thought I would share! (and of course you want to analyze the kind of music you enjoy or want to write)
Heres the sites:
http://icking-music-archive.org/ByComposer.phphttp://www.muslib.se/ebibliotek/boije/indexeng.htm 