Anyone who has seen the 1985 movie Re-Animator can tell you that H.P. Lovecraft's short stories are pretty much impossible to adapt to film. And Herbert West -- Reanimator, the story the movie is based on is one of Lovecraft's more straightforward works; it involves only humans.
The widely-known legendary difficulty in adapting Lovecraft hasn't stopped a wide array of directors from trying, though. Lovecraft stories have been made into radio plays, live stage shows, short films and feature-length movies. Pretty much all -- with the exception of the radio plays, in which HSW's own Jon Strickland has taken part somehow -- have failed miserably. Much better, is to create homage to the author's work, rather than work directly from the stories. Everyone from The Simpsons to Evil Dead have done well making some mention of the Necronomicon and the movies that are inspired by, rather than based on, Lovecraft, like John Carpenter's In the Mouth of Madness, tend to be the best of the bunch.
Intelligent Life's Jason Zinnoman has a nice article on just why the work of the man who set his stories in other dimensions and regularly described the monsters his characters invoked as "unnameable" may be forever locked in prose. You can read it here.
And feel to go ahead and tear me apart in the comment section below. [youtube=http://www.youtube.com/watch?v=gcVYjlB-ZrY&feature=related&w=610]