Adium Alternatives for Mac OS X

Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.

Trillian is a proprietary multiprotocol instant messaging application.

Psi is a free instant messaging application designed for the XMPP network (including Google Talk). Fast and lightweight, Psi is fully open-source and compatible with Windows, Linux, and Mac OS X.

Irssi is an IRC client program for Linux, FreeBSD, Mac OS X and Microsoft Windows.

Kopete is a multi-protocol, free software instant messaging client released as part of the KDE Software Compilation. Although it can run in numerous environments, it was designed for and integrates with the KDE Plasma Workspaces.

ICQ is an open source instant messaging software.

Quassel IRC, or Quassel, is a graphical, distributed, cross-platform IRC client.

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

iMessage is an instant messaging service.

Bitmessage is a decentralized, encrypted, peer-to-peer, trustless communications protocol that can be used by one person to send encrypted messages to another person, or to multiple subscribers.

Apache Spark is an open-source cluster-computing framework.

qutIM is free and open-source multiprotocol (ICQ, Jabber, Mail.Ru, IRC, VKontakte) instant messenger.

KakaoTalk (Korean: 카카오톡), or sometimes KaTalk, is a free mobile instant messaging application for smartphones with free text and free call features.

WeeChat is a free and open-source Internet Relay Chat client, which is designed to be light and fast.

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.

Tencent QQ (QQ) is an instant messaging software service.

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 Talk.

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

YakYak is a desktop chat client for Google Hangouts.