Pidgin

Pidgin is an open source messenger that combines many popular messenger clients (such as MSN, Google, Yahoo, ICQ, etc...) into one. It has a very clean interface and loads very fast. No spyware, adware, advertising, etc... And it also comes for many platforms such as Windows, MAC OSX, Fedora Core, CentOS / RHEL. It also supports plugins so you can add more messenger protocols, text encryption, etc... The only downside is that it does not support video and audio conversations.

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