Fearnet has a great, note-perfect choice of "10 Greatest Horror Movie Music Themes".
Myself, I am crazy about John Harrison's score for "Creepshow". Also: "Phantasm", "The Amityville Horror" (instant shudders from that music!)... and continuing that choir-like trend, "Children of the Corn".
I don't enjoy the "Friday the 13th" films, but Jason's musical cue is definitely a winner ("Kill!" "Ma!")
I also have a huge crush on Fantomas' "The Director's Cut", in which Mike Patton and esteemed friends re-interpret a bunch of film themes to crazed and wonderful effect. A number of choices are horror-related, not least "Ave Satani".