eboard is a chess interface for Unix-like systems (GNU/Linux, FreeBSD, Solaris, etc.) based on the GTK+ GUI toolkit. It provides a chess board interface to ICS (Internet Chess Servers) like FICS and to chess engines like GNU Chess, Sjeng and Crafty. The primary purpose of eboard is serving as interface to FICS, but also allows you to play against a chess program, analyze saved games, and play with other eboard user on the Internet. Eboard is developed by Felipe Bergo (fbergo at gmail dot com , and my handle at FICS is Pulga). eboard is Free Software, distributed under the terms of the GNU General Public License. Eboard provides many features other interfaces lack, like a good looking, configurable interface, multiple board views, resizeable board (without restarting), seek table, text input separated from the output, input history (bash-like), scripting, scroll lock, and many others. See the features section for a walk-through of eboard's features. Eboard development services are hosted by SourceForge. An FTP mirror of eboard and related files is kindly hosted by the SEUL project.

The JavaBoard is an easy to use interface for the American Free Internet Chess Server! This client is especially geared towards new users. More experienced users may find downloading an interface to connect with a better option, as it will offer more features.

Jin is an open source, cross platform, graphical client (interface) for the Internet Chess Club and the Free Internet Chess Server. It currently supports ICC and FICS but is designed to be able to support any chess server.

Knights aims to be the ultimate chess resource on your computer. Written for the K Desktop Environment, it's designed to be both friendly to new chess players and functional for Grand Masters. Here's a quick list of Knights' key features:

Play against yourself, against computer opponents, or against others over the Internet.
Customize your board and pieces with over 30 different themes, or create your own!
Audio cues help alert you to important events.
Novice players can preview potential moves.
Save your unfinished matches and play them again later.
Knights is OSI Certified Open Source Software and is licensed under the GNU General Public License.

XBoard and WinBoard are graphical user interfaces for chess. They display a chessboard on the screen, accept moves made with the mouse, and load and save games in Portable Game Notation (PGN). They serve as front-ends for many different chess services, including:

Chess engines that will run on your machine and play a game against you or help you analyze, such as GNU Chess, Crafty, or many others. A list of compatible engines is available.
Chess servers on the Internet, where you can connect to play chess with people from all over the world, watch other users play, or just hang out and chat. A list of compatible servers is available.
Correspondence chess played by electronic mail. The CMail program (which works with XBoard only) automates the tasks of parsing email from your opponent, playing his moves out on your board, and mailing your reply move after you've chosen it.
PGN viewer. You can use XBoard or WinBoard as a viewer and creator for game files recorded in PGN (standard chess notation).