I was trying to find some stuff and I came accross that movie shutter, that does sound good from what I heard.
as far as japanese horror I came accross that site
http://www.kyonsi.com/sitemap.htm that has some stuff that looks really cool. It has the movie "tale of two sisters" that patrick s just recomended, so he might want to check that out too.
one japanese director that I like is takashi miike. he's made like 60 movies and most of them suck, but there are some that are pretty cool. not all of them are horror some are more like crime/gangster, but all of them are usually pretty gruesome. the most famous ones are Audition and Ichi the killer, so you should probably go with those, and there's a few others on that site I posted.
He was a big inspiration for the movie Hostile, and he has a cameo in the film. The guy that did that movie (eli roth) also did Cabin Fever which is pretty good too.
another japanse movie that I wanted to see is called Tetsuo which is about a guy that finds his body turning into metal, but it's more like an artsy flick than straight up horror. I'm not sure who does that, but hes a couple other art/suspense movies that look pretty good.
Another pretty good horror flick is Susperia. I think it's italian. it's pretty artistic too, so I don't know if it's for everyone's taste.
There's some good mexican horror movies, but they totally escape me right now. Guilermo Del Toro who did the great Pan's Labyrinth (you should see it if you haven't) did a movie called the Devil's Backbone, that I want to see.
just one more off the top of my head, I liked pretty much all the movies that were based on the books by richard matheson. they aren't really that good, but they are pretty good, and I like them, just because the books are so good. those would be A Stir Of Echoes, the Omega Man, What Dreams May Come, Hell House (which i just now see hedonis mentioned)...
Peter Jackson has some good horror movies as well: Bad Taste, Frighteners, Dead Alive.
There's a pretty decent Australian zombie movie called "Undead."
I've neglected to mention classic american horror movies because the list would go on and on, and I wanted to bring up things that people might not have thought of.
oh yeah, and although it's not really horror either, i'd definetly recomend Stay. it's one of my favorite movies.