Someone's uploaded the 2001 movie "Dagon" to YouTube. It's a surprisingly faithful adaptation (not of "Dagon" as you might expect, but "The Shadow Over Innsmouth"), except their Innsmouth is in Spain, the protagonist isn't visiting intentionally, some events are swapped around, and it has a different ending. It's directed by the guy who made "Re-animator". You might enjoy it!
Ah cool. I feel a bit bad for seeing it for free now, so I'll have to buy the DVD. I've been meaning to see the black & white "Call of Cthulhu" and "Whisperer in the Darkness" since seeing their trailers, but unfortunately they've got no distribution in the UK.