Trillian is a proprietary multiprotocol instant messaging application.

Gajim is an instant messaging client for the XMPP protocol which uses the GTK+ toolkit.

Instantbird is a cross-platform instant messaging client based on Mozillas XULRunner and the open source library libpurple used in Pidgin.

Kadu is a free and open source multi-platform instant messaging client that supports Gadu-Gadu, XMPP IM networks and other services based on XMPP like Google …

Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.

Miranda NG is a successor of Miranda IM, a popular multi-protocol instant messaging client for Windows.

Psi is a cross-platform powerful XMPP/Jabber client (Qt, C++) designed for the Jabber power users. Psi+ is a development branch of Psi IM XMPP/Jabber client.

Coccinella is a free and open-source cross-platform client for the XMPP/Jabber-instant messaging-protocol.