https://dreamandcolor.com/ has been a fun solo bootstrapped side project for me for the past 2.5ish years - (specialize in converting photos to coloring pages for parents, educators, etc)

I started it primarily wanting to take a shot at productizing an image diffusion model (Stable Diffusion 1.5 when I started) in a novel (at the time) way and it ended up growing legs of it's own.

She's steadily chugging along, growing about 10-20% per month with minimal marketing, exceeding all expectations I had for the project when I set out