Sources of open data?

I'm looking for sites that host open data. It'd be nice if they were collaborative projects too, like a site that tracks prices of domestic-groceries that's updated by users. By "open" I don't mean monetarily-free, but rather data that is free from restrictive-licenses. A website that hosts free data, uploaded by its users, with the agreement that all data uploaded then belongs to the entity that hosts it is something I am not looking for. OpenStreetMap is a good example of what I'm looking for, I think... I'm under the impression the data uploaded by the user still belongs to the user. I may be mistaken though.

A cursory search found this website: https://library.bu.edu/bizdata/free-data . I haven't gone through the links on that page yet, but in case I can't find what I'm looking for there I thought I'd also ask users here.

Originally I wanted to find a repository of currency-conversion prices, but then I began to wonder about libre data repositories in general.