Here are a few major ones:
Bernard Herrmann - The Day the Earth Stood Still
Bernard Herrmann - Fahrenheit 451
Gil Melle - The Andromeda Strain
Jerry Goldsmith - Planet of the Apes
Jerry Goldsmith - Logan's Run (The film may not be so great, but the score is brilliant.)
Leith Stevens - Destination Moon
Leonard Rosenman - Fantastic Voyage
If we expand our list to include TV, I would add:
The Twilight Zone (esp. Herrmann, Goldsmith, Nathan Van Cleave)
The Outer Limits (season one, Dominic Frontiere)