Matrix is a federated chat protocol that allows users on different servers to talk to each other.
Rooms are mirrored on each server with a user in them, meaning all servers have to leave a room for it to disappear.
Riot is a client for Matrix, which runs entirely in the browser and can therefore be hosted on IPFS or simply downloaded and run via file path.
It can also be run as a desktop app.
Peertube is a video hosting platform built on ActivityPub and WebTorrent.
It uses WebTorrent to distribute videos between people watching them -thus taking the load off of the server- and ActivityPub to federate with platforms like Mastodon.
Pixelfed is a federated Instagram alternative that can also federate with Mastodon and Peertube.