Stick to the fundamentals, and stick to them harder
I've created https://www.kanochart.com to help product people create Kano surveys and analyses to prioritize their product roadmaps with.
I've gotten in touch with several of its users to better understand their needs and the feedback I get is generally favourable (and enlightening :)).
Of course, not everyone does a Kano survey every day, so the tool really is something that people use only once so very often.
I really want to attract more users, because I really enjoy building and improving the tool knowing that it's helping people out there build better products. I've joined some communities to drop a link to the tool whenever it seems relevant, but that's quite an intensive way of marketing what is basically a side project.
So how would you market a tool like this, knowing that it's currently free (meaning I don't want to spend money on advertising)?