Sadly, mostly due to the bizarre visual elements to some of his stories, he hasn't really had a spot on adaptation of his work. The silent short Call of Cthulu was excellent, but was far from a straightforward film. In the Mouth of Madness, a Carpenter film I love, is the best Lovecraft film, in my opinion, even if it was a riff on his stories rather than a direct translation. Stuart Gordon and Brian Yuzna have repeatedly dipped into those murky waters, with various degrees of success, such as Dagon and the Re-Animator series. My favorite of their forays is From Beyond, featuring a particularly maniacal Jeffrey Combs.
From Beyond centers around a pair of scientists attempting to stimulate the pineal gland with a device called The Resonator. An unforeseen result of their experiments is the ability to perceive creatures from another dimension that proceed to drag the head scientist into their world, who returns as a grotesque shape-changing monster and preys upon the others at the laboratory.
Past the jump is my favorite scene from a film packed with gruesome oddities. SPOILER! In the clip, Jeffrey Combs' body and mind have been horribly warped by the effects of the resonator. Naturally, he's developed a taste for human brains.
If you ever find yourself in a life or death, hand to hand battle, you might borrow from the book of Road House, but me? I'm gonna suck the other guy's eye out of its socket and feast on his brain. In the parlance of Mortal Kombat, "FATALITY." Sure, it's kind of gross, but no one will ever mess with you again.