WOW! Thanks for that list Gomez.
"The Unamable" did have one redeming feature. The Howard Carter? character, has a bit where his friend has just begged him to go back to the haunted house with him to find out why their friends didn't return from the house and the nominal "hero" replies something to the effect of "NO WAY! Those places are dangerous. If they're still there then they're already dead. I'm going home for the weekend."
I would put in another vote for "In the Mouth of Madness", while it ultimately failed at it's ambitious goal, it remains a fascinating failure. The references are much more to to King than Lovecraft, but the feel of the movie is defintely in the later's camp. The whole spreading madness theme is very Lovecraft as is the "knowledge driving you insane" thread and reality not really being what we think it is.
One movie that was not mentioned that I would add was the somewhat unfortunately named "She-Creature". No overt references to Lovecraft's stuff, but the story and the movie really do feel like they could have been written by HPL.
Plot Summary - Traveling circus encounters an old man the night before they are supposed to sail for america. Turns out old man has a captive mermaid, that has clearly made him somewhat less than sane. Seeing this as their big chance the leader of the circus (Rufus Sewell - Dark City), goes back to steal the mermaid that night during which the old man is accidentally killed. Sneaking the mermaid on board, it quickly becomes clear that she's not quite so helpless as the chains and tank would indicate. Also that she has a taste for human flesh. The wife of the circus leader meanwhile is increasingly tormented by nightmare images from the mermaid who has some kind of link with her. Finally, the whittled down crew is wiped out in an orgy of violence when the true form of the mermaid is revealed and the wife finds out why she was the only one spared...
"Cast a Deadly Spell" Is a very funny movie with enough little jokes and background events going on to place it up in the Airplane/Top Secret class. It's well worth the effort to track down, but I would have to disagree about the sequel "Witch Hunt" I felt it lost everything that made the first movie so much fun other than a handful of background jokes.