The subreddit has a lot of prompts for stories. Look for posts labeled with the "Prompt" flair. Some include what is effectively the first chapter of the story, but others are just the bare idea. I posted this one a couple of years ago that got some good responses:
Animagi are rare. This makes Padfoot a topic of much interest among the dogs, and he indulges their curiosity, letting them know about his life, his family, his friends, and his godson. When the Potters are betrayed, he uses the Twilight Bark to help track Pettigrew down. His confrontation with Pettigrew and subsequent arrest having been witnessed by a couple of the dogs who helped, the word goes out: "Padfoot can't take care of Harry; it's up to us!"
For those unfamiliar with the reference, or whose memory, like mine, is starting to slip the occasional gear, the Twilight Bark comes from "101 Dalmations." One of the responses to the prompt brought in a reference to "The Rescuers," which I thought was wonderful, and had not thought of.
