mastodon (twitter alternative)
pleroma (twitter alternative)
GNU social
PeerTube (jewtube alternative)
PixelFed (instagram alternative)
diaspora (faceberg alternative)
searx (metasearch engine)
yacy (p2p search engine)
Most of these can even federate with each other through ActivityPub (https://en.wikipedia.org/wiki/ActivityPub)
see https://en.wikipedia.org/wiki/Fediverse