Trillian
Freemium
Trillian is a proprietary multiprotocol instant messaging application.
IM+
Freemium
IM+ supports simultaneously major IM services, including Google Talk, Twitter DMs, Yahoo!, AIM/iChat, ICQ, Jabber (and Slack through Jabber), etc.
Matrix.org
Open Source
Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with…
Dialog Messenger
Free Personal
Dialog Messenger is a handy and feature-rich enterprise multi-device messenger available for server or cloud.
Jitsi
Open Source
Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.
ICQ
Free
ICQ is an open source instant messaging software.
Kiwi IRC
Open Source
KiwiI RC is a webIRC client.
Shout
Open Source
Shout is a self-hosted web IRC client.
Compare Pidgin with alternatives
Compare Dialog Messenger and Pidgin and decide which is most suitable for you.