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

Empathy is an instant messaging (IM) and voice over IP (VoIP) client which supports text, voice, video, file transfers, and inter-application communication ov…

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

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

Rambox is a free and Open Source messaging and emailing app that combines common web applications into one.

FlareGet is a download manager for Windows, Mac and Linux.

Trillian is a proprietary multiprotocol instant messaging application.

uGet is a GTK based Download Manager for GNU Linux and Windows.

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

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.

Finch is a console-based IM program that lets you sign on to AIM, Jabber, MSN, Yahoo!, and other IM networks. It runs on Unixes. It uses GLib and ncurses.

MLDonkey is an open source, multi-protocol, peer-to-peer file sharing application that runs as a back-end server application on many platforms.