Eboard Save
An interface for FICS. Quite featureful. GPL, Unix/Linux only.
http://eboard.sourceforge.net/   

ICC Interfaces Save
A thorough collection of Java, Windows, Macintosh and UNIX clients which will work correctly with the ICC chess server.
http://www.chessclub.com/interface/   

JavaBoard for FICS Save
A Java Applet allowing to play on the Free Internet Chess Server. Not very featureful, but gets the job done if you can't install an interface. Freeware, Platform independent.
http://www.freechess.org/javaboard/in...   

Knights Chess Interface Save
Knights is a relatively new graphical chess interface for KDE. It is, however, already quite featureful and very nice looking. Doubles as a chess engine front end. GPL, Unix (KDE) only.
http://knights.sourceforge.net/intro.php   

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