Libraries and Archives With Jewish Music Collections - http://www.jmwc.org/jmwc_libraries.html

This Web site is a treasure-trove of links to a huge number of sites containing information pertaining to Jewish music.  You can spend hours exploring the various descriptions of the many collections housed in these facilities.  This excellent reference site can be used for serious research of just for the fun of it. If you have any interest in Jewish music, be it classical, music of the Yiddish Theatre, Klezmer etc. this is the site to visit.