This is really good fun:

tilde.club is just a tiny tiny server running linux on the amazon cloud. Using tilde.club requires you to understand shells and ssh. If you don’t know about those things, consider this a challenge and opportunity to learn! This concludes the tutorial.

Paul Ford dipped into the creation on a MetaFilter thread:

Since a Unix box comes with mail, primitive server-wide broadcast chat, and person-to-person chat, this has turned into a de-facto social network in the same way that being on the early web was a de-facto social network. Except much, much cheaper than it used to be.