While I don't know of any such site, I wouldn't recommend it either.
Open source projects are made by the community, for the community, so I'd recommend you start by helping out one of the projects that you personally use. Maybe you can fix a bug that is bothering you, or implement a functionality that you are missing.
I also think its important to note the thing that wikipedia itself has an article about, which is that it is an encyclopedia.
You wouldn't cite the encyclopedia in a scientific paper, or even a university hand-in. It's just bad praxis. However, you would absolutely check the encyclopedia if you wanted to quickly gain a basis of knowledge on a topic.
The wikipedia one seems nuts to me. Like you literally can cross-check the sources if you think it is making a wrong claim.
People are quick to say "but everyone can modify it!" as if claims made by other souces arent made by basically random guys as well.
Found this thing yesterday. I've contributed to OSM more in a day than in the previous year. It's great.
Yup, you explained it much better than me!