Yahoo Messenger
Yahoo! Messenger is a popular instant messaging client and protocol provided by Yahoo!. Yahoo! Messenger is provided free of charge and can be downloaded and used with a generic "Yahoo! ID" which also allows access to other Yahoo! services, such as Yahoo! Mail, where users can be automatically notified when they receive new email. Yahoo instant messenger also includes a security feature which allows the user to be "invisible" to whoever they choose. In addition to instant messaging features similar to those offered by ICQ and AOL Instant Messenger, it also offers some unique features such as: IMVironments (customizing the look of Instant Message windows) and Custom Status Messages. Another recently added feature is customized avatars.
TweetDeck
TweetDeck is a social media dashboard application for management of Twitter and Facebook accounts. Like other Twitter applications it interfaces with the Twitter API to allow users to send and receive tweets and view profiles. It is the most popular Twitter application following only the official Twitter website. It is compatible with several operating systems including Microsoft Windows, Mac OS X, Chrome OS and Linux.
Trillian
Trillian is a multi protocol instant messaging application for Windows created by Cerulean Studios that can connect to multiple IM programs from one client, such as AIM, ICQ, MSN Messenger, Yahoo! Messenger, IRC, Novell GroupWise Messenger, Bonjour, and Jabber and Skype networks (the latter four with Trillian Pro which allows for additional plug-ins).
Skype
Skype is a little program for making free calls over the internet to anyone else who also has Skype. It’s free and easy to download and use, and works with most computers. Now it also supports video conferencing over the net.
Pidgin Messenger
Gaim is a multi-protocol instant messaging (IM) client for Linux, BSD, MacOS X, and Windows. It is compatible with AIM and ICQ (Oscar protocol), MSN Messenger, Yahoo!, IRC, Jabber, Gadu-Gadu, SILC, GroupWise Messenger, and Zephyr networks. Gaim users can log in to multiple accounts on multiple IM networks simultaneously. This means that you can be chatting with friends on AOL Instant Messenger, talking to a friend on Yahoo Messenger, and sitting in an IRC channel all at the same time. Gaim supports many features of the various networks, such as file transfer, away messages, typing notification, and MSN window closing notification. It also goes beyond that and provides many unique features. A few popular features are Buddy Pounces, which give the ability to notify you, send a message, play a sound, or run a program when a specific buddy goes away, signs online, or returns from idle; and plugins, consisting of text replacement, a buddy ticker, extended message notification, iconify on away, spell checking, tabbed conversations, and more.
Nimbuzz Messenger
Nimbuzz Messenger combines the power of internet and smart phone messenger into one, and lets you make free video calls, voice calls, send chat messages, make new friends in chat rooms and share files on any PC/mobile device across popular messengers. Connect your address book and share unlimited photos, make unlimited audio calls & video calls, share files, music and videos with other friends of yours on Nimbuzz, Facebook, Yahoo Messenger, Live Messenger (MSN) and Gtalk. You can also connect with your friends on Twitter using our popular chat buddy. Nimbuzz Features
MSN (Live) Messenger
Windows Live Messenger (formerly named MSN Messenger) is an instant messaging client created by Microsoft that is currently designed to work with Windows XP, Windows Vista, Windows 7, and Windows Mobile. The client has been part of Microsoft's Windows Live set of online services since 2005. It connects to Microsoft's .NET Messenger Service. The client was first released as MSN Messenger on July 22, 1999, and as Windows Live Messenger on December 13, 2005. The service attracts over 330 million active users each month.
mIRC
IRC (Internet Relay Chat) is a virtual meeting place where people from all over the world can meet and talk; you'll find the whole diversity of human interests, ideas, and issues here, and you'll be able to participate in group discussions on one of the many thousands of IRC channels, on hundreds of IRC networks, or just talk in private to family or friends, wherever they are in the world.
Miranda
Miranda Instant Messenger is a minimalistic, free open source (GNU GPL) multiprotocol instant messaging application for Microsoft Windows. Miranda provides a basic client framework and an advanced plugin architecture. Support for various IM protocols and additional features is implemented through optional plugins, some of which come bundled with Miranda by default while the rest can be downloaded from the Miranda IM website. This keeps Miranda lean and fast, since unused protocols can be removed. There are currently over 500 plugins for Miranda.
ICQ
ICQ is an instant messaging computer program, created by Mirabilis, an Israeli start-up company based in Tel-Aviv. The program was first released in November, 1996. The name ICQ is a play on the phrase "I seek you".