@feditips It's awesome! There's even so many more that it's impossible to list them all!
Lemmy (https://join-lemmy.org/), an alternative to Reddit.
Pleroma (https://pleroma.social/), a lightweight microblogging network (like Mastodon, but with some differences).
Plume (https://joinplu.me/), a federated blogging system.
Misskey (https://misskey.page/), an extra-fully featured microblogging server.
And so many others!
See https://fediverse.party/ for even more examples.
For people who care about, support, or build Free, Libre, and Open Source Software (FLOSS).