Monsters Anonymous

So you have a setting where non-human beings exist, and their nature makes living among humans difficult. Maybe they suffer from a Horror Hunger, live forever (and it sucks), have customs that don't endear them to locals (such as rampant kleptomania and throwing around Curses like it's going out of style) and/or the stress of keeping up the Masquerade is just brutal. Well, there's a support group of reformed/reforming monsters that is out to help those among them who want to live closer to humanity. Possibly even to regain some of that humanity if they were human once. They may even help convince a newly turned member he isn't human at all.

The status of this group in monster society can vary. They may be a bunch of Defectors From Decadence and Pro Human Transhumans who are actively hated by their society at large, a fairly neutrally viewed group, or they may even be top dogs and are enforcing the Masquerade via these groups as a form of positive self-policing (with another group in charge of chasing down those who "relapse"). You often get groups of Friendly Neighborhood Vampires forming these kinds of groups, though a group of Fully Embraced Fiends may form such a group to help fledgling Vampire Refugees adjust without going all Hunter of His Own Kind.

They'll typically help each other deal with mundane and magical matters, like how to ensure their Undead Tax Exemption, keep their Horror Hunger at bay, mask the smell of brimstone/rotting flesh, how to fool human social customs, etc. That said, it's also possible for these groups to focus on blending in not for humane reasons (no pun intended), but to better prey on humans, in which case "disposing of bodies" is usually also on the list of things they help each other do.

Contrast Fully-Embraced Fiend. Usually at the "acceptance" phase in the Stages of Monster Grief.

Anime and Manga:

 * In Rosario + Vampire, Yokai Academy teaches monster children to hide themselves from humans, and helps them live alongside muggles by remaining in human form and attending a school designed to resemble a human boarding school.

Comics

 * The living fairy tales in the comic Fables establish a regimented and regulated community to prevent their discovery while living in New York city.
 * The real movie monsters of Screamland are a twisted version of this.

Film

 * The sharks' support group in Finding Nemo. "Fish are friends, not food!"

Literature

 * The Black Ribboners on the Discworld are a strong example of the Friendly Neighborhood Vampire type.
 * In Fevre Dream by George R. R. Martin, there's a vampire who's found a way of surviving without drinking blood, and he's travelling around gathering up other vampires and persuading them to make the same lifestyle change.

Live Action TV

 * Mitchell in Being Human (UK) very explicitly uses the Support Group strategy to convince all the vampires in the city to stop drinking human blood (and killing to keep it quiet) and go clean. (In this setting, vampires don't need to drink blood, but abstaining causes incredible hunger pains akin to drug withdrawal until they can psychologically adjust). Amazingly, it works! Of course,
 * In the NBC show Grimm Monroe, Nick's monster friend, has gone through a "program" so as not to be a Big Bad Wolf anymore. He had at least one friend we've met who went through the program with him.
 * In The Middleman, Roxy Wasserman is a reformed succubus who runs a halfway house for not-quite-reformed succubi, disguised as a fashion boutique.

Tabletop RPG

 * The RPG Nightlife has the Commune, a multi-species alliance of monstrous creatures that work to live in relative peace with humanity.
 * Although every The World of Darkness series gameline has shades of this, it's most notable in Vampire: The Masquerade, Werewolf: The Apocalypse, Promethean: The Created and Changeling: The Lost.

Western Animation

 * The Department of Integration on Ugly Americans, a government agency that prepares monsters (and human immigrants) for life in New York City. The main character, Mark Lilly, is a human social worker employed by the Department; his co-worker Leonard is a wizard, and his superiors are demons.