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.
Out of curiosity rather than necessity, are there any activitypub based messaging apps (i.e matrix/discord-like)?
One not listed is Ibis (https://ibis.wiki/) which hasn't had much traction. Honestly unsure of how useful it is as a direct wikipedia replacement but i can see it as a cool idea for a bunch of related communities that would otherwise be on separate wikis.
Ibis is really early days. I hosted it for a bit and had things like federation issues and softlocks. Will be really interesting when it's a bit more mature though.