Socialhome with its tiled display of posts
Bonfire, which is modular, and will be available in many flavours (for Open Science, organisations or simply a social network)
Mobilizon - events and groups.
Gancio - events, published anonymously. Instance can be followed from Fediverse as an account.
Bookwyrm for books
Postmarks - a federated bookmarking website
Funkwhale - for uploading and listening to music
Castopod - Wordpress but for podcasting?
Misskey and its forks - more than Twitter emulation - includes emoji reactions and animated text!