I second Dead Silence and Mirrors. Those are two of the scarier movies out there. I like the original Japanese One Missed Call a lot too.

I'm excited for the week-end. I'll be snuggling on bed with my wife and watch a lot of those movies.

I watched Altitude. It is not scary and not a great movie but it's an interesting enough of a premise and a twist for a watch.

Darkness. Maybe not a terrifying movie, but its ambiance is really great.
Blair Witch Project (a classic imo)

Also, I wouldn't recommend Dead Silence. The acting, the story, the characters, and god that final plot twist are the worst...

If you're into it, Dario Argento's movies are nice too, but let's say they didn't age so well...

The Lady In Black has an amazing atmosphere and some really tense moments

Jacob's Ladder is an absolute masterpiece. Maybe not a "horror" movie, more like a psychological thriller, but if you like Silent Hill, you'll love it.

The Children is pretty neat, not great but it does the work. Also, you won't see children the same way anymore.

The Mist is great. Like, really great. And the ending is quite a punch in the face. Loved it.

And the last one I'd recommend is From Within. Not a masterpiece either, but it's a decent movie.

Some movies i forgot everything, man, it's too tough to remember.

The Exorcist, The Ring, The Grudge, House on Haunted Hill (1959), The Blair Witch Project? :S, The Sixth Sense

The original Omen, not the remake.