Here are some of Debbie's favorite links for a variety of things relating to violin and music:

Sheet Music:
http://www.freesheetmusic.net/
http://www.gmd.de/Misc/Music/scores/Introduction.html
http://www.musicianspage.com/home.html
http://www.musicaviva.com/
http://scriptorium.lib.duke.edu/sheetmusic/
http://www.hnh.com/mgloss.htm
http://www.danmansmusic.com/index.htm
http://www.rainmusic.com/pianomusic/free.htm
http://www.vvoss.freeserve.co.uk/index.html
http://www.virtualsheetmusic.com/Home.html

Catalogs:
http://www.johnson-inst.com/catalog/index2.htm
http://www.sharmusic.com/html/fid.html
http://www.violinsetc.com/shop/home.asp?inexid=4KKS2HH2D6
http://www.orchestralstrings.com/bows.htm
http://www.altieribags.com/
http://www.themusichouse.com/musich/index.html

Chamber Music:
http://www.acmp.net/

Violins:
http://www.fritz-reuter.com/
http://www.gregsandow.com/ (excellent articles)
http://members.nbci.com/mrfiddle/
http://www.fritz-reuter.com/howtobuy/index.htm
http://www.culturevulture.net/Movies/RedViolin.htm
http://library.thinkquest.org/27178/en/index.html
http://www.violink.com/ (one of the best link pages around)
http://www.bright.net/~hhelser/practice.html

Home Pages:
http://www-openmap.bbn.com/users/gkeith/fiddles/Fiddle.html
http://www.bright.net/~hhelser/index.html
http://determan.net/Michele/fiddle.htm

Music:
http://classicalmus.hispeed.com/
http://www.musictheory.halifax.ns.ca/index.html#lesson
http://members.aol.com/Kitchiegal/kmmusic2.html