DinoModern XMPP ("Jabber") Chat Client using GTK+/Vala
Chatsecure IosChatSecure is a free and open source encrypted chat client for iOS that supports OTR and OMEMO encryption over XMPP.
pluginsOfficially supported Psi plugins
stork(M) Android XMPP Client
Lurch4AdiumOMEMO Xtra for Adium (packaging the lurch and carbons libpurple plugins)