Spinning Spinny Thing – Link
This is a single generator with a massive number of options. Limit your prompt to specific, pre-existing universes, include existing characters, objects, emotions, trigger warnings, genres and a whole lot more! This generator also allows you to create a permalink to your prompt, allowing you to share it with others.
Seventh Sanctum – Link
A massive database of generators. Create plots, story elements, creature designs from unique half-breeds to intricately described dragons, character and place names, systems of magic, mechas, and loads more. Each category of generator has a whole page of things to play with.
Springhole.net – Link
This website has loads of different prompt generators sorted into categories. Use prompts to design characters, create plots, costumes, settings, anything you might need to create a story. The plot generators are incredibly varied, with random generators, genre-specific random generators, fairy-tale generators, creepypasta generators… and more!
Age of Fable – Link
This is a simple, single page prompt generator that lets you narrow the prompts by genre, and will produce any number of single-sentence story prompts for you to work from. Simple, to the point and provides a nice, structured prompt.
TV Tropes – Link
TV Tropes generator provides links to random tropes to use as plot, setting, narrative device etc. It’s a fun and somewhat different approach to prompt generators, leaving you with a lot of creative freedom. Great for people looking for a writing challenge more than a cure for writer’s block.
Fiction Generator – Link
A simple, single-button generator that produces individual, details prompts, along with a title for the work. Quite fun, and with a lot of variety in the sort of prompts that generate. Titles and story prompts have a dstinctly steampunk feel to them, although they blend magic, technology, time travel and settings from throughout history.
Chaotic Shiny – Link
Another huge website with dozens of generators, from arc generators, plot generators, name, item, location… you could build a plot and an entire universe to go with it from here.