How are you hosting? Renting a physical box? Using something like AWS?
Physical boxes tend to be expensive, but you have more control. Something like AWS maybe cheaper, but it’s hard to control your costs.
Diaspora – as someone else mentioned – seems to be the simplest way. However, I thought that relied on a single person hosting their “pod”, or multiple people agreeing to host a pod. You’re essentially running a single instance of a web server, that can “see” the other web server instances. You control what you want to see, but I don’t know how distributed it is. For example, I don’t know if you can host the same web server serving up the same content using multiple machines without any load balancing, or replication.
Happy to be wrong about Diaspora though. Signed up in the early days, but completely forgot about it for ages. Seems like it is ready for mainstream use now though.