Some very good answers in this post: I’m aware of kbin, mastodon, and lemmy. Are there any other federated applications out there? : nostupidquestions, some random copy&paste:

Here’s a list of 130: https://the-federation.info/#projects

this diagram

From What other kinds of servers are on the Fediverse? | Fedi.Tips – An Unofficial Guide to Mastodon and the Fediverse:

As well as Mastodon, there are lots of other server types on the Fediverse, for example:

• BookWyrm – A social reading platform, an alternative to Amazon’s GoodReads

• Friendica – A general social network with no character limits, sort of like Facebook used to be on its older interface

• Funkwhale – Music and podcast storage and sharing

• 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

• WordPress – Independently hosted WordPress blogs can be turned into Fediverse servers using a special plugin

• WriteFreely – Minimalist blog where focus is on the text, like a calmer version of Medium

…and that’s just some of them! If you’re a techy person, you can see more comprehensive lists of server types at FediDB and delightful fediverse apps.