Let us not forget the ever dreadful Boo.

Coma (1978)
Jacobs Ladder...in a strange kind of way it does
Dead Ringers (1988)
Resident Evil
The Ambulance (1990)
Patrick (1978)
The Sender (1982)
Anatomie 2 (2003)
Visiting Hours (1982)
Bad Dreams (1988)
Hospital Massacre (1982)

...not all of them are only at a hospital

I don't think that was actually in a hospital. Villian's a doctor in a castle/mansion, I think they just call it hospital.

Hey now. I liked Boo. Granted, it's not going to win any awards or anything.:)

There's the Japanese movie Infection. I think the entire movie is set in a hospital.

Nightmare on Elm Street 3

Yeah true, the doctor's mansion was where he performed his experiments.

The first one that comes to mind is Candy Stripers and that is fairly new. Came out like a week or two ago.

Fragile

Day Of The Dead 2: Contagion took place in a mental hospital. close enough...not worth watching though.

Return of the Living Dead pt.2
Halloween 6 (Mental Hospital)