Cast a Deadly Spell was that Fred Ward movie, which directly referenced the Cthulhu mythos. Thing is, it didn't really have much of the mood or feel of Lovecraft's work at all - it was a comedy, essentially.
Films that have a Lovecraftian feel:
The Wicker Man
The Exorcist, and Exorcist 3 (although 3 was a dumb film, it had some great atmosphere)
Carnival of Souls
Evil Dead - the first one especially has the feel, because Lovecraft's work is maked by a distinct lack of humor, but Evil Dead II and Army of Darkness both have very Lovecraftian elements
The Devil's Bride aka The Devil Rides Out