Trillian is a proprietary multiprotocol instant messaging application.

Franz is a free messaging app /former emperor of Austria, that combines chat & messaging services into one application.

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

AIM is a instat messenger application.

Facebook Messenger is the official Facebook app that lets you have text conversations with all of your friends on the popular social network.

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

Smuxi is a cross-platform IRC client for the GNOME desktop inspired by Irssi.