A petition has been created to try and convince Sony to release an official Silent Hill Movie OST.

http://www.petitionspot.com/petitions/getsilenthillost

Even though it probably won't work, you never know, so please sign it. Even better, if anyone is a member of various Silent Hill fansites/forums, please let them know about this petition. The more people who sign it, the better!
Thanks for your support.