My #Fediverse ideas that I'm not going to build, but I'd love to see someone build.
1) "fedevent": a platform specifically for events. You could follow venues, artists/facilitators/teachers, as well as hashtags. Easy links to registration/ticketing.
2) "fedigroup": a platform for group discussion where each group can choose what's published or not (group existence, posts that start conversations, individual comments, members, etc.)