First of all, Film Score Monthly now has its own domain name, http://www.filmscoremonthly.com. You're here right now!
The single best film music web site is http://www.filmmusic.com. Here you can find links to all the other film music sites, both professional and fan, as well as links to retailers, search engines for soundtrack albums, and a whole bunch of other stuff.
The one Usenet newsgroup dedicated to film music is rec.music.movies. Discussion is often, shall we say, limited, but lively.
There is also a mailing list for film music discussion, "Filmus-L." When you sign up, messages from participants will arrive directly in your mailbox. Send to email@example.com to subscribe and write in the body of the e-mail, SUB FILMUS-L (for example, SUB FILMUS-L Joshua Feldman).