I only got into Lovecraft very recently, in the past few years. Rats in the walls is a great one, by the way.

It can be a bit of a nusiance to have to wade through some of the dross of his pulp material to find the REALLY chilling stories, but they're definately worth it.

And he is, of course, most famous for the Cthulhu Mythos. I saw a while back that a fan community had made a 1910s/1920s style silent movie of The Call of Cthulhu, and it looked to be a wonderful rendition of the story.

A computer game (Call of Cthulhu: Dark Corners of the Earth) also showed some of the same love and devotion to the source material. The game's based around The Shadow of Innsmouth, and some scenes in the game are perfect reproductions.