Streaming Media:www.naxosmusiclibrary.comIs there a piece of classical music that you desperately want to hear? you'll find it at Naxos.
www.bbc.co.uk/radio3/discoveringmusic/audioarchive.shtmlBBC Discovering Music Archive: An excellent resource for beginners and experienced listeners alike, with illustrated audio talks on a wide range of composers and pieces.
www.columbia.edu/itc/music/reserves/Columbia University Music Reserves, the selection is limited, but the recordings are excellent.
http://www.archive.org/Contains massive amounts of documents, videos, and audio, although the quality is somewhat questionable.
http://classical.comnot as good as Naxos, but decent enough to deserve a mention.
Sheetmusicwww.dlib.indiana.edu/variations/scores/Looking for the scores of Bruckner's 9th? you'll find it here.
www.imslp.orgLooking for free scores?
Biographies/Music LearningWikipedia.comA good place to read about composers that you don't know. Wikipedia has very good biographies and links.
www.musictheory.netA good place to learn the basics of music theory, the first step of becoming a composer.
www.grovemusic.coma website to find biographies on composers, however, Wikipedia actually contains more informations on composers than this site.