pmmg
Myth Weaver
As someone who's at the point where I'm looking for critiques, I found Betareader.io to be the best site for finding beta readers so far, so it comes with its share of challenges. The free version gets you three beta reader slots, but you can gain more by reading other peoples' works (or by paying $10 per month). I got over 20 interested readers in a few days. It's frustrating only having 3 readers slots with so many applicants, but once your figure out the messaging system you can draw additional readers to your own copies of your manuscript.
Has anyone else found a good tool for finding beta readers?
No, I have some beta readers, but you never really have enough
Scribophile has a karma system, but it will get you reviews if you put in the effort. I look at what you posted.