The Argus-eyed Mitchell Porter points me to Jason Colavito's argument, in From Cthulhu to Cloning, that Lovecraft was a decisive influence on the ancient-astronaut wing of crank archaeology, and so on such modern movements as the Raelians. Which is obvious, in retrospect: Lovecraft has lots of bogums which came to Earth from Someplace Else, and were worshipped by human beings --- some of them are hinted to have made human beings, more or less as a joke. And this was not a common theme before him; it would be surprising if the ancient-astronauters hadn't gotten the idea from Lovecraft. But Colavito lays out positive reasons to think this happened, including amusing textual evidence.
Colavito doesn't seem to remark on it, but it's interesting to note how the myth has changed as it moved from person to person, and especially how it's become more comforting and conformable to mainstream religion. In Lovecraft, the Old Ones aren't even malign --- they are so alien that our moral terms no more apply to them than to hurricanes or solar flares. In the first generation of ancient astronaut writers, say von Daniken, the motives of the aliens are ambiguous, or are mixed, but they have motives. When one descends to the generation of Rael, not only are the aliens basically benevolent, they're wrapped up in the Christ story. (One of the first things I wrote for the Internet argued that Cthulhu was in part a satire of Christ. I still buy that, though I hope I don't write like that any more.) That is, the story been transformed by passing through minds brought up on Christianity. I'm sure there are more Lovecraftian variants circulating, but they're obvious vastly less fit, i.e., less popular.
Of course, just because something is a fantasy out of Lovecraft doesn't mean it can't happen. "Insane cult performs weird, pointless experiments on human beings" deserves to be on the
Dystopian Millenial Checklist, but it happens every few years now. Maybe the Old Ones are coming.