- A text mode menu- and window-driven instant messaging interface that supports the ICQ, Yahoo!, AIM, MSN, IRC, XMPP, LiveJournal, and Gadu-Gadu protocols. A continuation of Centericq. Latest release is 4.22.10, 2010-11-23.
- An open source groupware platform which includes email, calendaring & scheduling, address books, bulletin boards, mailing list server, instant messaging, and multiple domain support.
- A cross-platform Jabber client. Key features include an integrated whiteboard, P2P file transfer, multilingual support, group chat, secured connections (TLS and SASL), and an open standard instant messaging protocol (can connect to any Jabber/XMPP instant messaging server). Coccinella is the Latin name for ladybug.
- An instant messaging client for GNOME. Latest release is 0.31, 2009-07-14.
- A KDE instant messenger; a flexible and extensible multi-protocol system suitable for personal and enterprise use.
- An ICQ/AIM clone written in C++. It uses an extensive plugin system to manage many different functions including the MSN protocol. Latest release is 1.3.6, 2008-10-02.
- This instant messaging application allows private conversations by providing encryption, authentication, deniability, and perfect forward secrecy (if private keys are compromised, no previous conversation is compromised)
Pidgin- IM Client
- A cross-platform, multi-protocol instant messaging (IM) client for GNOME. Excellent multilingual support -- 72+ languages available. Formerly called Gaim. Latest stable release is 2.6.5, 2010-01-08.
Psi Jabber Client
- A cross-platform, open source instant messaging software built on the Jabber protocol.
- An open source ICQ client. Latest release is 0.9.4.3, 2007-04-04.