Mastodon - my main social feed platform that first introduced me to the Fediverse in general.
Lemmy - my second main social feed platform that originally substituted Reddit from years ago.
Matrix protocol - communication platform I use to connect with users on the Lemmy instance I'm on
Peertube - would love to get an account going and use it more often but still don't know how but there's FediVideo.
Bookwyrm - Goodreads alternative that I signed up for that could use more work for a genuine reading tracker.
BONUS: my least favorite Fediverse platform lately
WordPress - because I used to run art blogs on there before I heard word about drama about the CEO of the corporation so I basically had to put out my last existing art blog...RIP.
I really wanted to like bookwyrm and use it but it's just so bare bones.
Instead, I switched from goodreads to StoryGraph like two years ago.
I really like some of its features like content warnings, moods, very detailed stats of my reading habits, etc.