Ask HN: How do small developer promote own apps?

[DarkwingDuckFan]

If you’re a small developer (with no or just small marketing budget) and creates a genius app for a special problem, how do you promote the app? Ok, Website with SEO. And Social Media is a channel, but this will keep mostly in your own bubble. Which directories, press services or others do you use to tell the public your app exist? What kind of other ideas do you use?

[cc101]

Online/offline communities for special problems are very difficult to find. Ideas for finding them would be a useful answer to this question.

[taubek]

If it solves a special problem, maybe there are online/offline communities of people that are troubled by that problem?

[DarkwingDuckFan]

Yes, that's an obvious solution. But what other ideas are out there to publishing? I am sure some websites are good multipliers to spread a new tool, but which websites & services?