I can't, because none of them have a public point of presence on the internet. That's rather part of the point of doing it -- to keep the internet at arm's length. They're all, effectively, invite-only since they serve groups of people who are already known to each other.

Some do this on a small scale, like operating a VPN and a series of services accessible over the VPN. Others on a larger scale, like running what amounts to a small ISP and communal servers.

If you're into the idea, it isn't be that hard to get things going on the technical side, if you use the internet itself as your "dumb pipe communications channel". You just need some friends who are interested in joining you.