Neterarti runs GNU social and I'm part of that project so in terms of federated social media software I'm a bit biased. There's great stuff like https://blog.p2pfoundation.net/first-distributed-tool-new-sharing-economy/2016/03/23 being built on GNU social. Diaspora still has a lot of love, and the W3C is working on social network federation interop, so we can all grow our decentralized communities and I hope we all win.