You can try kickstarter. Last time I checked KS, these kinds of projects (e.g. I'm writing fairy tales for kids who loves mathematics, etc.) were the most popul

You can try kickstarter. Last time I checked KS, these kinds of projects (e.g. I'm writing fairy tales for kids who loves mathematics, etc.) were the most popular. The problem is that you'll be forced[1] to deliver something on schedule and might stop feeling like a hobby project and more like a job, so make sure you don't take more than you can chew. [1]: This is not 100% accurate, but you catch my drift.