Kbin – Link aggregation and discussion, sort of like Reddit
Mobilizon – Event organisation, the Fedi’s alternative to Facebook Events
OwnCast – Video livestreaming with a chat window at the side, very much in the style of Twitch
PeerTube – YouTube-style video sharing site which uses P2P technology to allow even small servers to have videos go viral, as the more people view a video the more bandwidth it gets
PixelFed – Photo sharing site, similar in style to Instagram and Tumblr