Diaspora was meant to be it - launched in 2010 it had one million users by 2014 (according to the wikipedia page). I can't find numbers for current active user counts, but it didn't win much mindshare, by any measure.
FreedomBox was being pushed heavily by Eben Moglen and Bdale Garbee (I saw them doing a FOSDEM presentation on this back in 2011) but it was more about the hardware platform (to support a free software social network suite) but it's also not really very popular, unfortunately.
Mastodon, as freehunter notes, is well known, but only in niche circles - and seems to be positioning itself as a twitter-alike only.
Searches for 'free software social network' will return a huge list of projects, but even for the most popular <sic>, federated, relatively painless to setup & maintain (or with paid hosted options available) systems ... the network effect combined with most people's inertia / apathy / ignorance means we're not going to be ridding the world of FB any time soon.