LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
featured
Redinfinite
Tumblr
BAZO
Mastodon
Reddit
Pillowfort
Fandomers
Den.social
Identi.ca
ColdCast
GNU social
Pleroma
ZeroMe
YouWeb
Youllo
Fritter
RedinfiniteTumblr - A feature rich and free blog hosting platform offering professional and fully customizable templates, bookmarklets, photos, mobile apps, and social network integration.
ColdCast - An open social network with zero corporate interference.
BAZO - Personalized welcome prompts for your website
GNU social - GNU social is communication software for both public and private communications.
Mastodon - Mastodon is a decentralized, open source social network. This is just one part of the network, run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome!
Pleroma - Pleroma is a free, federated social networking server built on open protocols.