I know this isn't exactly a list, but I'm looking for the list of essential horror movies that Stephen King put in the end of his book Danse Macabre. is there any way I could find this online?

Certainly.

You can ask us, then we go hunting around online, find an old message board post here (I googled danse macabre horror movies list and it was the fifth one down), and then copy the list from the board over here like so.  (I really need to read that book some time.)

The Abominable Dr. Phibes (1971)
Alien (1979)
Asylum (1972)
The Bad Seed (1956)
The Birds (1963)
The Bird with the Crystal Plumage (1969)
Black Sunday (1961)
The Brood (1979)
Burnt Offerings (1976)
Burn Witch Burn (1962)
The Cage (?)
Carrie (1976)
The Conqueror Worm (1968)
Creature from the Black Lagoon (1954)
The Creeping Unknown (1955)
Curse of the Demon (1957)
The Day of the Triffids (1963)
Dawn of the Dead (1979)
The Deadly Bees (1967)
Deep Red (1975)
Deliverance (1972)
Dementia-13 (1963)
Diabolique (1955)
Doctor Terror's House of Horrors (1965)
Don't Look Now (1973)
Duel (1971)
Enemy From Space (1957)
Eraserhead (1977)
The Exorcist (1973)
The Exterminating Angel (1963)
Eye of the Cat (1969)
The Fly (1958)
Frenzy (1972)
The Fury (1978)
Gorgo (1961)
Halloween (1978)
The Haunting (1963)
The H-Man (1958)
Horrors of the Black Museum (1959)
Hour of the Wolf (1967)
The House that Dripped Blood (1970)
Hush...Hush, Sweet Charlotte (1965)
I Bury the Living (1958)
The Incredible Shrinking Man (1957)
Invasion of the Body Snatchers (1956)
Invasion of the Body Snatchers (1978)
I Saw What You Did (1965)
It Came From Outer Space (1953)
It! The Terror from Beyond Space (1958)
Jaws (1975)
The Killer Shrews (1959)
Last Summer (1969)
Let's Scare Jessica to Death (1971)
Macabre (1958)
Martin (1977)
The Masque of the Red Death (1964)
Night Must Fall (1964)
The Night of the Hunter (1955)
Night of the Living Dead (1968)
Not of This Earth (1956)
No Way to Treat a Lady (1968)
Panic in the Year Zero (1962)
Picnic at Hanging Rock (1978)
The Pit and the Pendulum (1961)
Psycho (1960)
Rabid (1976)
Race with the Devil (1975)
Repulsion (1965)
Rituals (1978)
Rosemary's Baby (1968)
Salem's Lot (1979)
Seance on a Wet Afternoon (1964)
Seizure (1975)
The Seventh Seal (1956)
Sisters (1973)
The Shining (1980)
The Shout (1979)
Somebody's Watching Me (1978)
The Stepford Wives (1975)
Strait-Jacket (1964)
Suddenly Last Summer (1960)
Suspiria (1977)
The Texas Chainsaw Massacre (1974)
Them! (1954)
They Came from Within (1975)
The Thing (1951)
The Tomb of Ligeia (1965)
Trilogy of Terror (1975)
Village of the Damned (1960)
Wait Until Dark (1967)
What Ever Happened to Baby Jane? (1961)
When Michael Calls (1971)
The Wicker Man (1973)
Willard (1971)
X - The Man with the X-Ray Eyes (1963)
X the Unknown (1956)

Great, thanks!! Yeah, I'm kind of an idiot with which search words I use when I'm googling around. Thanks a lot!

My pleasure.  Always happy to be of service.