None for that only that are free. All I know of is some that LOOk like they're free and aren't. I signed up for one, and was not exactly delighted to find that a certain desperate gentleman from my past was looking for me, LOL. Another had a GREAT idea for an invention, all he wanted for me was to figure out how specifically to do it. And I was going to be allowed to do that for free, lucky me.
There are, though, ways to find people without signing up for a paying site. I used to be really good at digging up people. Lately, it's gotten far, far easier as so many people have a presence on facebook or similar sites.
It really helps to know the person's interests, as many interests have small communities, and there are only a handful of websites the person might be chatting on. And if the person has a profession or product s/he markets, s/he's likely to have a web page advertising that.
Contacting former mutual friends is another avenue. If there's a school reunion committee that's another route.