Music Composers Unite!
I recently came across a site I hadn't known about, Musical Chairs, which people on this site may be interested in. It has not only a list of calls for scores, but also a section for buying and selling instruments, and (something I've never seen before) a section where people can post notices of instruments that have been stolen. The latter makes rather depressing reading, and I'm not sure how much good it will do to post a notice that your instrument has been stolen there, but I suppose it couldn't hurt.
I have no connection with the site and don't know anything more about it than I've said here; I just thought some other people may be interested in it.