Boson  
   A real-time Linux strategy game for two players. (Open Source, GNU GPL)
   http://boson.eu.org/

Advanced Strategic Command  
   A turn based strategy game for Linux or Windows. (Open Source)
   http://www.asc-hq.org/

Attal: Lords of Doom  
   Turn-based strategy game for Linux in which you control bases and manage fighting lords.
   http://attal.sourceforge.net/en_pages/en2_nt_news.shtml

The General  
   Turned based military strategy game for Windows in which you control a nation. Your goal is to unite the world under your rule, upon conquering all the other states.
   http://newgame.agava.ru/eng/g_news.html

Phobia III  
   Choose your weapon and tactics to slaughter as many of the aliens that swarm you as possible. Features stunning graphics for Windows or Linux.
   http://www.lynxlabs.com/phobiaIII/

Constellation!  
   Constellation is a 2D turn-based pure-multiplayer strategy / combat game for Windows with a space theme. Well suited to be played by email.
   http://groups.msn.com/Constellation/_whatsnew.msnw?pgmarket=en-us

Boa game  
   A multi-player clone of the worm(6). Includes, server, client, and bot. Source can be compiled for SGI, Linux, Sun or Gnuwin32.
   http://www.tarunz.org/~vassilii/pub/boa/

CivQuest  
   Turn-based Civilization clone written in Java. (Open Source, GNU GPL)
   http://civquest.sourceforge.net

Pocket Civ  
   Turn-based Civilization clone for Palm OS.
   http://geocities.com/icepirates2/pocketciv.html

C-evo  
   Turn-based empire building strategy game for Windows. (Open Source)
   http://www.c-evo.org

Planetasia  
   Space strategy game for Windows.
   http://planetasia.freecyberzone.com

Overlord '44  
   Overlord '44 is a 3D real-time strategy game about the D-Day landings. You will command either the Allies trying to get further inland or the Axis trying to repel the Allies.
   http://www.freewebs.com/overlord1944/

The Colonization II Project  
   Project to create an alternative sequel to the turn-based strategy game Colonization by Sid Meier.
   http://www.civgaming.net/col2

FreeRails  
   Multiplayer real-time strategy game inspired by Railroad Tycoon and Railroad Tycoon II. Written in both C++ and Java. (Open Source, GNU GPL)
   http://freerails.sourceforge.net

Castle Combat  
   A clone of Rampart for Linux. Two players build castle walls, place cannons inside these walls, and shoot at the walls of their enemies.
   http://user.cs.tu-berlin.de/~karlb/castle-combat/

L-O-C  
   Turn-based strategy game with some strong RPG elements, based on a game by Julian Gollop. Runs under MS-DOS, Windows and Linux by using an Atari emulator. (Open Source, GNU GPL)
   http://l-o-c.sourceforge.net

Cult  
   Using negotiation and trade, one must resolve a situation involving cultists barricaded in a villa two kilometers away from town. (Windows)
   http://www.studio-blum.com/cult/

Marbles  
   Create figures out of single marbles. One-way streets, crumbling walls and portals make the task interesting. (Linux)
   http://lgames.sourceforge.net/index.php?project=Marbles

Scorched Island 3D  
   Combines tactics from popular game Scorch and elements from RPG games for DOS or Linux.
   http://cvs.linux.hr/si3d/

UFO 2000  
   A multiplayer remake of X-COM: UFO Defense for Windows. (Open Source)
   http://ufo2000.sourceforge.net/

Crimson Fields  
   Describes tactical war game for Linux or FreeBSD in the tradition of Battle Isle. Two players command their units on a map of hexagons, trying to defend important locations to destroy all enemy forces. (Open Source)
   http://crimson.seul.org/

Glest  
   Single player, 3D, realtime strategy for Windows with up to three computer opponents.
   http://www.glest.org/

Emperor of the Fading Suns: Hyperion  
   A patch by Matt Caspermeyer for the turn-based game. Includes download, documentation, tutorials, and a forum.
   http://www.twarriors.com/~hyperion/

The Battle for Wesnoth  
   A turn-based game with a fantasy theme. Includes download, project information, FAQs and manual, screenshots, and a forum.
   http://www.wesnoth.org/

SantaGames.co.uk  
   Contains "Santa's Snowy Workshop" available for download. [Windows All]
   http://freespace.virgin.net/tim.wintle/santagames/