Here are some good links our members have collected over the past few years with lots of free sheet music for classical guitar.  While much of the music on these sites is "free" in the sense that you do not have to pay to download it, and some of it is also free of all copyright, much of it is only made available under licences which place some restrictions on what you can do with it.

http://www.free-scores.com/free-sheet-music.php?CATEGORIE=999
A site with the widest range of free sheet music for the classical
guitar that I have so far found,

Conditions of use: Various, depending on the item. Details of the various licences applicable are given (in French only) on the licence page.  

http://www.dailyguitar.com/Sheet-Music/

A site dedicated to all the guitarists . Learn about the composers, find more things about many guitarists, get information about the classical guitar competitions,

download free scores / tabs and recording.

http://www.yatesguitar.com/scores.html
Transcriptions by Richard Yates.

Conditions of use: The only condition specified is that anyone downloading the PDF files take a look at  the page describing Yate's published transcriptions.

http://coheym.hp.infoseek.co.jp/
Kouhei Minami's homepage with links to free copies of his original works and transcriptions.

Conditions of use: "Only the copy of those other than the nonprofit purpose is permitted.  The copyright of the contents of this site is in me." (I wouldn't take the first of these statements literally—it is clearly intended to permit only non-profit use.)

http://gallarda.narod.ru/
"Classical Guitar Big Archive" of the Russian guitar society.

Conditions of use: The materials "may be used only in the purposes of education.  They are not for commercial using."

http://members.home.nl/mark.erna/text_en/solo_s.html
DOS Amigos Home Page.

Conditions of use: The home page states that scores available for downloading are all in the public domain (i.e. free of copyright).

http://www.hebeonline.com/lists/authors.htm
Hebeonline has works of Carcassi, Coste, Giuliani and Sor and others  available. Many, including most of Sor's studies, Giuliani's opus 48  studies, and some of Carcassi's opus 60 studies are available free to anyone.  You can get the rest if you become a subscriber.

Conditions of use: Copyright of files is owned by Tecla Editions  The site's FAQs state that copies can be made "only for your own use and for use in classes and performances in which you are yourself a participant."

http://www.delcamp.net/en/index.html
Delcamp's classical guitar scores, forum, mp3s, videos & online
lessons.

Conditions of use: "Scores, online guitar lessons, audio and/or video documents found on delcamp.net are free and royalty free and may be used for non-commercial and individual purpose. You are not authorized to distribute one or more copies of any of the above mentioned, in native or converted format. Provided you are a guitar teacher and a registered user on delcamp.net's forums, you are authorized to give away printed copies of scores to students who do not have internet access. In such case, the help you provide to our forums' users compensates for these free scores. In the event one would cease to participate in the forum(s) and stop helping members, one will have to stop using delcamp.net documents."

http://classicalguitar.homeip.net/Sheetmusic.htm
David's classical guitar site.

Conditions of use: None stated in any obvious place. 

http://www.eythorsson.com/en/ 

Eythor Thorlaksson and Sveinn Eythorsson's Guitar School, Iceland's site.

Conditions of use: PDF files can be downloaded freely, printed for personal use and photocopied for students, but may not be further distributed without permission.