TPPC
A Pokemon-like game with unlimited levels and player forums.
Free to play indefinitely.
http://tppcrpg.net/
Trackmania Nations
Smooth racing game with good graphics.
Free to play indefinitely.
http://www.trackmanianations.com/indexUk.php
Travian
Travian is a browser based MMOG where you can compete with thousands of other players by taking control of a small village and leading your people to glory and victory.
Free, with option to pay for additional features.
http://www.travian.com
Tremulous
In this sci-fi combat game you can choose to play a human soldier using a range of weapons and armor to fend off the alien menace... or play as an alien, using your bite, claws, speed and poison to eliminate the humans.
Free to play indefinitely.
http://tremulous.net
Tribal Wars
In Tribal Wars, your goal is to lead a medieval village to fame and power. You do this by upgrading your village’s buildings, gathering resources and plundering other villages controlled by players.
Free, with option to pay for additional features.
http://www.tribalwars.net/
Trickster Online
Anime themed RPG much like Maple Story or Runescape. Impressive graphics, skills, and monsters.
Free to play indefinitely.
http://www.tricksteronline.com/
Twelve Sky
Twelve Sky is an oriental style, martial arts based MMORPG with strong PVP. Features realistic martial arts weapons and moves.
Free to play indefinitely.
http://12-sky.aeriagames.com/
Uniball
Spaceships playing a sort of soccer-like sport.
Free to play indefinitely.
http://homepage.ntlworld.com/jamie.mac1/uniball/
Unification Wars
Unification Wars is a free online strategy game with over 350,000 members. You are the leader of your civilization, and your goal is to expand the power of your empire by diplomatic or military means.
Free, with option to pay for additional features.
http://uc.gamestotal.com/
Urban Dead
Make your way through derelict buildings and fend off the legions of the undead in this massively multiplayer zombie apocalypse.
Free to play indefinitely.
http://www.urbandead.com
Urban Terror
Urban Terror can be described as a Hollywood tactical shooter; it is realistic to a certain extent, but the creators go by the motto "fun over realism."
Free to play indefinitely.
http://www.urbanterror.net/
Vega Strike
"Vegastrike is an OpenSource 3d Space Simulator. Currently in Beta developement, the project, at version 1.0, is to be a generic space simulator. Current features include split-screen play, trading, exploration and of course plenty of shoot 'em up action."
Free to play indefinitely.
http://vegastrike.sourceforge.net/
Virtual Family Kingdom
Create your own character, room and friends! You can also play lots of minigames to win in-game currency which will buy you stuff to dress your characters or items to furnish your room. Similar to Disney's Virtual Magic Kingdom.
Free to play indefinitely.
http://www.virtualfamilykingdom.com
Virtual Magic Kingdom
Quests, magic, chgat, and adventure in a magical world based on Disney's theme parks.
Free to play indefinitely.
http://www.vmk.com/
Voyage Century
A beautiful MMORPG with a strong community, set in the days of pirates and voyages. Be a Merchant or Craftsman, conquer unknown lands or fight against pirates!
Free to play indefinitely.
http://vc.igg.com/
vSide
"vSide users configure their own avatars, make friends, chat, dance, listen to music, shop for clothing, attend events and parties, create and decorate their own private spaces, and throw their own parties in those spaces, choosing the music, videos, and guest list."
Free to play indefinitely.
http://vside.com
War of Conquest
A highly addicitive strategy war game with cash prizes. Develop your nation, form alliances, research technologies, and fight battles over resources and the mysterious orbs scattered throughout the enormous game world. The longer you hold an orb, the more money you win.
Free, with option to pay for additional features.
http://www.warofconquest.com/
Warrock
"War Rock is an exciting military, multiplayer, online FPS that combines large scale vehicle combat, adrenaline pumping team combat and special ops close quarters combat all in one game."
Free to play indefinitely.
http://warrock.net/
Water Margin
Set in the era of the Song Dynasty, character classes include Monk, Major, Taoist and more. Water Margin is a well known novel from China.
Free to play indefinitely.
http://www.108.com.my/
Well of Souls
"Well of Souls is a multi-player Role Playing Game (RPG). It is designed to be extensible through a simple scripting language so that you can compose your own quests and share them with your friends. You can also customize your skin and contribute art and music."
Free to play indefinitely.
http://www.synthetic-reality.com/wosHome.htm
Wizard101
A wizard school adventure with collectible card magic and wizard duels. The game allows players to create a student wizard in an attempt to save Wizard City.
Free, with option to pay for additional features.
http://www.wizard101.com
WolfTeam
A first person shooter where you can play a soldier or a wolf. The objective is to wipe out the opposing team or to take over the enemy base.
Free, with option to pay for additional features.
http://wolfteam.softnyx.net/
Wonderland Online
Free 2D MMORPG based on several ancient South American and Pacific Island cultures. Combines elements of fantasy and sci-fi with nature magic, spaceships, item creation, house customization and more!
Free to play indefinitely.
http://wl.igg.com/
Wulfram II
"In a place and time far away from where we are today, two intergalactic forces fight for control over a few strategic planets. In large antigravity hovertanks battle lines are being drawn. A commander controls mammoth spaceships orbiting far above the battlefield. New temporary military bases are being built as the enemy is destroying old ones. The goal? Complete annihilation of the enemy. Welcome to Wulfram II, welcome to the struggle of your life."
Free to play indefinitely.
http://www.wulfram.com/
Wyvern
"Wyvern is a multiplayer action/role-playing game similar to a text-based MUD (or "Multi-User Dungeon"), but Wyvern also has a graphical view of the game. Wyvern is a special game - if you make Wizard, you can create your own game worlds for other people to visit."
Free to play indefinitely.
http://www.cabochon.com/
Xiah
Xiah is an asian martial arts MMORPG with four classes to choose from. The game is mainly based on combat and there are unique ways of developing your character.
Free to play indefinitely.
http://xiah.gamescampus.com/
Zero Online
Play a pilot and master high-tech weapons while fighting in an immense sci-fi universe. Shuttling between several galaxies, you pilot units with various forms and functions to fight against ferocious alien enemies.
Free, with option to pay for additional features.
http://zo.91.com
Zu Online
Chinese fantasy based MMORPG with 5 classes, pets, and guilds. Takes place in the Mystical Zu Mountain range.
Free to play indefinitely.
http://zu.igg.com/
Zwinky
Customize your look and clothing, meet friends, play mini-games and much more in this addictive social game.
Free, with option to pay for additional features.
http://www.zwinky.com/