Would try to target communities that align with your target audience - Twitter, Subreddits, Facebook groups, or Discord. Can also promote more generally on some of these platforms or ProductHunt
Another method, guerilla testing, worked well in grad school. Go to a public place - a library, coffee shop, etc. Politely ask random people to test your project. The obvious downside is they may not fit your target audience, but it's a cheap and scrappy way to get some feedback.
muzani
Who's the target market? You should be able to find a persona of someone interested in it. Even if you built it for yourself, you should be able to make a persona that's a fragment of yourself, e.g. Jay who puts all his MMO stuff on spreadsheets and wants to migrate his sheets to a wiki.
Where do they hang out? That's probably a good place to start.
solardev
There's Uservoice and Mechanical Turk too, if you want a more general audience
The_Colonel
1) build something which could be interesting to other people
2) make threshold to test the product and post feedback low (e. g. GitHub)
3) promote it on HN, reddit, producthunt...
4) people will test and some will report bugs / submit ideas etc.
maxbaines
Perhaps post some details here? As Show HN.
mcsniff
The fact that you don't realize you can post here, in this very community, really should give some pause.
polygot
What would you like to have tested? I might have time to provide some feedback.
Kirtirajsinh
Look out for Communities on Discord, telegram with whom your product aligns.
Another method, guerilla testing, worked well in grad school. Go to a public place - a library, coffee shop, etc. Politely ask random people to test your project. The obvious downside is they may not fit your target audience, but it's a cheap and scrappy way to get some feedback.