Here are some of the links that have given me some great insight into the world of motion picture soundtracks:

http://www.moviemusic.com

http://www.moviesounds.com

http://www.classicalrecordings.com

http://www.cinemusic.net

http://www.musicfromthemovies.com/

also there are the base sources like

http://www.imdb.com which is the internet movie database, about the greatest internet movie site on the planet

and of course, the very commercial amazon.com, which does have a very large catalogue of works. I hope all of those links are helpful in some way. I've been collecting film music for many years, but have slacked off in the past decade, mostly due to time. I find that as I grow in age, some things grow less important. I knew a man in Hollywood who dedicate his whole life to film soundtracks. He had an entire room that was filled with recordings most librarians would be drooling over. But I also discovered that despite the fact that having all this made his collection very valuable, he was shallow, very superficial, and lacked practically any redeeming value as a human being. Like "Kane", we can amass all the things we can buy, but cash cannot buy lifelong friends, intregrity, or humility. Hollywood and New York are filled with forgotten "has beens" that lack all of those qualities, because they believed in only themselves, and not in the ideals we all treasure as worth having.

I apologize for pontificating.