Almost all monster movies take as a starting premise that few people know or believe that such things can exist. A handful like the TV series Special Unit 2 have a small cadre of people who know, but the general public doesn’t. Has anyone done a story (film, tv, novel) where it’s commonly known that there really are undead, aliens, monsters, etc?
Just off the top of my head, in Kim Newman’s series, vampires are pretty well known, especially after Vlad Tepes defeated the evil Dr. van Helsing and married Victoria…
Do you mean recently (ie, modern Western space-age culture)? You don’t have to go back very far to a time when the existence of ghosts, demons, witches, and such was commonly accepted.
Most comics take place in worlds where superheros and villains, and monsters, demons, aliens etc. are well known to the public.
Frankly I always thought Buffy would have made more sense if the general public was aware of what was going on. By the end of Angel they practically were.
… for the novels/plays, I mean. Obviously, Shakespeare’s screenplays are rare.
But off the top of my head: Harry Potter
In Steakley’s ‘Vampire$’ (the book that John Carpenter’s Vampires was VERY loosely based on), the existence of vampires does not appear to be a secret. When the vampire hunters are called in by the local authorities to clean out an infestation, the town gathers around to watch and there appears to be no attempt to cover itup.
In the “Anita Blake: Vampire Hunter” books by Laurell K. Hamilton, everyone knows that vampires exists. I thought the first 4 or 5 books were quite good.
I think they kinda played with the idea that most people knew what was going on. Once the musician Aimee Mann was playing that club/bar they used to hang out in, and she said something like “I hate playing vampire towns…”
I can’t recall the name of the episode, but when Buffy is awarded the special title of “Class Protector” the presenter’s speech explicitly states what many of the episodes hinted at-the general public doesn’t want to know, and spends most of its time in denial.
Back To The OP
There are plenty of comics that fit your description. While in the film, Hellboy’s existence is a secret, in the original comics he was front page news when the UN held a special session to determine if he was legally human and entitled to human rights. He goes out in public dressed in shorts and a BPRD jacket. Abe Sapien, however, does wear concealing clothing and latex masks when in public. He’s never gotten used to people staring, and most people can’t handle the fact that his facial structures display emotion differently than a human face.
WitchHunt- This film with Dennis Hopper is a hardboiled detective story set in a world in which magic has (apparently recently) become public knowledge.
In one of the movies, where the kids are in the flying car, they get yelled at for almost being spotted by Muggles. If everyone knows about magic, what would be the issue?
Yeah, but there’s many examples of the general public NOT knowing, or at least not being expected to know.
In the first episode of Buffy Xander overhears Giles amnd Buffy talking about vampires, and his reaction is WHAT?
In the first episode of Angel there’s an exchange that goes rou8ghly along the lines:
Cordy : Hey, there’s no mirrors in this room … oh my God, you’re a vampire.
Vampire : (surprised) You know about us?
**Cordy : ** I come frome Sunnydale.
In the episode where the Angel gand revert to teenagers Wesley is ready to reveal the big secret that Vampires are real, and is surprised when Gumnn knows already.
Ryk Spoor’s Digital Knight involves the public finding out about monsters among us.
Well, I guess I Am Legend probably doesn’t count, since Robert N. is the last human. Lost boys plays with the idea at the last line in the movie You know the all the damned vampires comment, right?
If you count human monsters (ie. serial killers and such whatknot) tehn movies like From Hell definately know what’s going on. As a matter of fact, I think most serial killer movies present themselves in this way. The best exception I can think of is Citizen X, the story of Andrei Chikatilo (sp?).
I guess if you are going for the entire human race knowing there is something strange going on, then X-Men would be your best bet. You can’t (or maybe you can, depending on your view of things) really consider most of them monsters. But I think this might best fit your bill.
CS Friedman’s Coldfire Trilogy involves a world where
the environment itself spawns exactly what you fear
It’s a very well-written series and I cannot recommend it enough.
The general public becomes aware of Graboids by Tremors 2 in the Tremors series. There are even comic books and games that are based around them.
In John Crisopher’s Tripod series, everyone knows about the tripods, they just don’t know what or who powers them.
The entire Alien Nation franchise was about the interaction of humans with Newcomers.
Cast a Deadly Spell is an interesting take on the hardboiled detective tale. There’s wizardry, demons and a unicorn or two.
Kim Newman’s Anno Dracula series and Laurell Hamilton’s Anita Blake series are probably the two best known examples of the “open vampire” genre. Two others that haven’t been mentioned are Brian Stableford’s The Empire of Fear and Kristine Kathryn Rusch’s Sins of the Blood.
There were a couple Lovecraft semi-parody movies, at least one of which had a bunch of zombies assembling a house. Someone makes a comment about how everyone know zombie-built houses are crap but all the companies use them since the revivification process was discovered in the early 20th century, or something like that.
Cast a Deadly Spell, and its aforementioned, re-cast, and generally inferior sequel, Witchhunt.
Well, for the sake of completeness, in Piers Anthony’s “incarnation of immortality” books, the existence of magic and mythological creatures is commonly accepted across the world, in the equivalent of a late 20th century culture.
The hot smoke dragons are a federally protected endangered species, IIRC. 
Not really in the monster/horror genre I know.