1) Nuclear - Desktop music player focused on streaming from free sources (in beta phase):
Nuclear Mastodon account: @nuclear
2) Pidgin - IM with options to add various third party plugins which enables you to use facebook chat, steam chat, etc, XMPP included.
3) Synchting - cross platform peer to peer file synchronization, also available on f-droid:
And I forgot another one! 😀
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.