There has been a great ongoing thread on Anandtech dealing with freely available games.
Check the thread for updates
http://forums.anandtech.com/messageview.aspx?catid=33&threadid=1207656&enterthread=y
Contributed by randumb
Wolfenstein: Enemy Territory - World War 2 shooter
America's Army - Army shooter
GunBound - Worms clone
Freeciv - Civilization clone
Vega Strike - Space trader RPG
Frozen Bubble - Arcade game
Cube - Simple shooter
Legends - Tribes clone
Scorched Earth 3D - 3D Scorched Earth clone
Cannon Smash - Ping pong game
LGeneral - Panzer General clone
Armagetron - 3D Tron Clone
FooBillard - Pool
TEG - Risk clone
Hidden and Dangerous Deluxe 2 - World War 2 shooter
Grand Theft Auto - Original Grand Theft Auto
Cosmic Rift - Space ship fighter game
Contributed by Nohr
GeneRally - top down arcade racer
Stair Dismount & Truck Dismount - a couple cool games
Warblade - Galaga type game, the beta version is still free
Contributed by diegoalcatraz, links from CGW
Abuse 2 - Shooter based on 1995 original
Ancient Domains of Mystery - Huge RPG
Beneath A Steel Sky - Sci-fi adventure
Blip and Bop: Balls of Steel - Side scroller action
Colossus - Avalon Hill's Titan board game clone
Falcon's Eye - Graphical Nethack clone
Little Fighter 2 - Mortal Kombat style deathmatch
Notrium - Single player survival game
Steel Panthers: World at War - World War 2 RTS
Orbiter - Space flight simulation
Pekka Kana 2 - Side scroller action
Stick Soldiers 2 - Stick fighting game
The Ardennes Offensive - Action game based on the Battle of the Bulge
Vantage Master Online - Simulation RPG
Wazzal - Space privateering game
Contributed by Mloot
Subspace/Continuum - Space ship fighter game
Contributed by John P.
Warbirds III - WWII flight sim
Dawn of Aces III - WWI flight sim
Armored Assault - Tank sim
Contributed by igowerf
Dink Smallwood - Zelda-like isometric RPG
Ground Control - A great RTS game.
Contributed by M0oG0oGaiPan
Final Fallacy for RPGMaker 2000 - Huge RPG
Tetrinet - Puzzle game
Runescape - A free online rpg. You can play right from your browser or you can dl their small client app. Actually you can become a paid member and you get access to extra features but you are required to p2p.
Contributed by jimmyl930
Nethack - Rogue-like game
Super Bubble Blob - Platformer/Puzzle. Very challenging and fun.
Tetrinet 2 - Good tetris game
Flight of the Amazon Queen - Adventure game for ScummVM
Contributed by Maetryx
Angband - The spiritual descendent of the Rogue-like game, Moria. This is a "graphical" random dungeon, turn based game. You are represented by an '@' and the monsters in the dungeon are represented by letters (S = spiders, R = reptile, c = canine, o = orc, h = humanoid, H = giant humanoid). You can find potions (!), scrolls (?), rings (=), weapons (variously represented by the pipe and slashes). It is basically a Tolkien themed, single person, turn based, random dungeon game. And there are dozens of variations including sci-fi, Zelazney's Amber series.... etc.
Contributed by jjsole
Jardinains - A great pong/breakout game. There's a new version 1.2 that I've yet to try, looks nicer and more rich than 1.0.
Contributed by Jadow
Betrayal at Krondor - The CLASSIC rpg from Sierra in 1993 is available for free. When Sierra released their horrible quasi sequel Betrayal in Antara (no relation to the Krondor storyline) they released Krondor for free. It was about a 12 meg zip file to download. I know it can be found on the web still. While its an 11 year old dos game, BaK is one of the best RPG's ever made. Also, it was a very early try at being 3d (polygonal landscapes and mountains) and the graphics really, aren't that bad.
Contributed by QueBert
Icy Towers - This game is so basic, but I am stuck playing it! I love the theme music too.
Elastomania! - This is only a demo, but this is by far one of the most addicting and frustrating games I've ever seen. I got my Neices & Nephew hooked on it.
Clickomania! - I lub teh computar intarweb machen. A good puzzle game, has so many configuration options. I play for a week then change up the settings to make it like a whole new game.
Contributed by Jennerstein
One Must Fall 2097 - The old PC Fighting Game Classic.
King's Quest 1 - The Old King's Quest Classics remade by the Anonymous Game Developers.
King's Quest 2 - The Old King's Quest Classics remade by the Anonymous Game Developers.
Contributed by davidrees
Ultima IV - Arguably the best ultima game of all. If you have not played it and you like RPGs, you MUST play this game. It runs in DOS, but I think it works ok in a DOS box on modern versions of windows. I had a job once where I had to sit around for weeks waiting for something to break - passed the time with Ultima IV (and V which I owned).
Contributed by ArchStudent
Think Tanks - This is a pretty fun game/demo to play
Contributed by DannyBoy
Neocron MMORPG - This is a pretty fun game/demo to playHas a 10 day free-trial for those interested
Contributed by ViciouS
Unreal Tournament 2004 Demo - Is an awesome free game beta so its not quit a demo. Kool Vehicles awesome weapons and pretty stable for a Beta! Multiplayer and i think some single player.
Contributed by Mem
Unreal UFO-Alien Invasion - Is similar to the original X-COM UFO Defense game,the final full version will also be free as well, uses modded Q2 engine with resolution up to 1600x1200,so any turn based or X-com fans check it out.
Contributed by cw42
Allegiance - Allegiance was dev by Microsoft. It's a decent space shooter game.
Contributed by TimboAA
Tibia - A free MMORPG. My brother and his friend are playing it, I'm yet to try it out. Top view style game. Free, with the option to upgrade to a premium account for $$
Contributed by Firus
Soldat - Sweet 'Worms' style shooter with ragdoll physics, well worth the price
Contributed by Fuelrod
Zork I, Zork II, and Zork III - Classic text adventure games
Contributed by thornc
Pathological - Nice game written in Python!
Contributed by Da3dalus
Highway Pursuit - Really cool racing game with a bit of shooting
Contributed by Schadenfroh
Elder Scrolls: Arena - Great RPG
BZFlag - Great tank FPS game with CTF focus.
Contributed by Davegod
Tribes and Tribes 2 - The highly popular fps shooter, now released for free in anticipation of the release of Tribes: Vengeance.
Contributed by biostud666
Duke Nukem 3D - The popular classic FPS Duke Nukem 3D.
Contributed by Confused
Racer - A free cross-platform car simulation project (for non-commercial use), using professional car physics papers to achieve a realistic feeling. Cars, tracks and such can be created relatively easy (compared to other, more closed, driving simulations). Editors and support programs are also available to get a very customizable and expandable simulator. OpenGL is used for rendering. Pretty good simulation, with quite an established user-base, and lots of 3rd party cars/tracks.
Contributed by thenerdguy
Star Wars Games - A bunch of Star Wars Trilogy based games.
Contributed by so
Sim City Classic Live - An online version of the classic Sim City game.
Contributed by microAmp
Apple II Games - A collection of 1100 classic Apple II games.
Contributed by bockchow
Project Entropia - free MMORPG. well it's mostly free you have the option of buying in game money with real world money and it makes starting out alot faster. the money system is kinda odd in that you can transfer game money into real money buy depositing it into your bank acount. not the best game out but realy good for a freeish game.
Contributed by jjj807
Redemption Online - free version of Ragnorok Online.
Contributed by globemonkey
3D Tetris - free 3d tetris
Contributed by peetabix
PlaneShift - Now in puplic Beta, this is a completely free MMORPG. From the site The objective of the PlaneShift Team is to create a virtual fantasy world in which a player can start as a peasant in search of fame and become a hero. We will focus our efforts in the reproduction of a real world with politics, economy, many non-player-characters controlled by the server that will bring to life our world even without players connected!
FlightGear - FlightGear is an OpenSource flight sim. It includes over 20k real world airports and accurate terrain.
BillardGL - A billards sim in OpenGL.
TORCS - The Open Racing Car Simulator - A Racing sim that uses OpenGL. Next version will probably include multiplayer.
Wulfram II - A strategic online multiplayer fps, kinda thing. From the site It is a multiplayer, action-strategy game, that allows up to 64 players per server. Superficially speaking, the game is similar to that of Tanarus and perhaps Battlezone.
Void - This game is in its alpha stages. Void is a space RPG with four races.
Carom3d - A billards, pool and Snooker sim. From the site Carom 3D is an online multi-user billiard game created with special 3D graphic effects bringing every aspects such as 6 ball, 9 ball, 8 ball and others of Billiard game to life.
MegaMek - From the site MegaMek is an unofficial, online version of the Classic BattleTech board game. MegaMek is programmed in Java and will run on any system with a compatible Java Virtual Machine. It has been tested on Windows, Linux and MacOS X.
GLtron - A 3d tron clone in OpenGL.
Reaper - A 3D combat sim.
Pristontale - A free 3d MMORPG, featuring a free floating camera and a class change system giving you more freedom.
Dark Signs - From the site Welcome to the home of Dark Signs, the first advanced console based hacking game! Simply, Dark Signs is a game which simulates a network environment. It allows you to play as a computer systems hacker or cracker. Dark Signs has many advanced features.
Bontago - Bontãgo stretches the limits of strategy gaming by providing an innovative experience that will challenge even the most seasoned gamers. Construct towers to expand influence and control an ever changing playing field.
Open Zelda - Open Zelda is an open source 2D scriptable game engine. While many types of games can be made, the main focus is to make zelda like games. There are missions/games that you can download from the website.
Netkar - Basic racing sim in beta form. You MUST have an analog controller, as keyboard is not supported.
Secrets of Mirage - A free MMORPG.
Endless Online - Imagine a world where everything is possible! A place where you can become rich and famous or fight evil monsters and become a hero.. Or just a normal peasant life as a citizen...Endless is a mmorpg under development where you can do all this and more !
Dismount - Feeling nasty, mean and evil? Score points for causing pain to this poor guy.
Liquid War - A very original game. You control an army of liquid and have to try and eat your opponents. A single player mode is available, but the game is definitely designed to be multiplayer, and has network support.
Bygfoot Football Manager - A small and simple graphical football (a.k.a. soccer) manager game featuring many internat. leagues & cups. You manage a team from one such league: you form the team, buy & sell players, get promoted or relegated and of course try to be successful.
StepMainia - StepMania is a music/rhythm game. The player presses different buttons in time to the music and to note patterns that scroll across the screen. Features 3D graphics, visualizations, support for gamepads/dance pads, a step recording mode, and more!
OpenTTD - An open source clone of the Microprose game Transport Tycoon Deluxe.
Lincity - Lincity is a city simulation game. Build your city up from a primitive village to an advanced civilization. Build a sustainable economy, or build rockets to escape from a pollution ridden and resource starved planet.
Carworld - CarWorld is a small driving simulator in 3D.
Neverball - Tilt the floor to roll a ball through an obstacle course before time runs out. Neverball is part puzzle game, part action game, and entirely a test of skill. In 3D.
Skyscraper - The goal of the Skyscraper Project is to create a fully featured building simulation engine, including gaming support (single and network multiplayer).
Layout Ultimate 2004: Ultimate Frisbee - Yes, thats right a frisbee sim. It features 2v2 frisbee with simultaneous control of the thrower and receiver, and an assortment of modes and features, including ice mode.
Magebane 2 - Magebane 2 is a single player strategic roleplaying game where you command three monks on a quest to recover the holy Amulet of Yendor. Each monk masters a different school of magic, and you must find a balance in upgrading your skills in order to defeat your numerous enemies. Also, you can find various items to enhance your abilities.
Mojotron - Mojotron is an action game for Linux/X Windows inspired by Robotron and Llamatron. Also has a 2 player mode.
Warning Forever - A fast paced shootem' up.
Kaiser Kitty - Shift gravity to avoid traps and recover the legendary Kitty Edge from the clutches of the Intergalactic Guild of Evil Space Pirates. Puzzle/platformer.
Fish Fillets - Fish Fillets is strictly a puzzle game. The goal in every of the seventy levels is always the same: find a safe way out.
Tango Strike - An evil Tango army has risen to power, and it is up to your small team of secret agent operatives to shut them down.
Metroid Redemption - A metroid clone. 2d platform/side scroller.
Machines of Destruction - Machines of Destruction is mixture of racing through a circuit and wasting your opponents with a combination of the guns mounted on your car, best played on a LAN.
Kingdoms Of War - Online RTS.
Babylon5: I've Found Her - B5:IFH is a 3d space sim based on the B5 universe with Newtonian physics and a hyperspace that you have to navigate in or you will get lost. Decent graphics and piloting a Starfury can be demanding in newtonian mode.
Space Shuttle Sim
Gekkeiju Online - Gekkeiju Online is a Fantasy/Anime based 3d Multi-user dungeon. Currently in Open Beta.
The Universal - The Universal is big, it's constantly evolving and it's sometimes very strange...but it's always a free, massively multiplayer online game with a different experience on every planet you visit.