tent.io looks like the best alternative to centralized social networks at the moment. It seems to be really focussed on sharing stuff, while setup of your own server looks straight-forward. Similar to e-mail, as they state. Definitely something I will try out in the near future.
About me
My name is Peter Bouda and I am a software developer with more than 20 years of professional experience in application development. I help you to bring your application to market as quickly as possible.