There's nothing like Asian horror movies when you want to get the crap scared out of you :P
The original Japanese versions of The Ring (Ringu) and The Grudge (Ju-on) are awesome, but the movie you should watch is called Shutter. (
http://www.imdb.com/title/tt0440803/) You'll be surprised how effective it is. Oh, by the way, don't watch the Hollywood remake: it sucks.