Free PC Gaming Blog posted an article which covers a huge list of 100 Games which you can download online for free and legal
Here is the list
Allegiance
America’s Army
Anarchy Online
Armada Online
Assault Cube
Bang Howdy
BloodLust Multiplayer Online Vampire RPG
BOTS
BZFlag
CodeRED: Alien Arena
Conquer Online
Corum
Cube 2
Cube
Daimonin
Dark Space
Darkeden
Darsana
D-Day Normandy
Deicide
Digital Paint: Paintball 2
Dungeon Runners
Entropia Universe
Eternal Wraith
F.E.A.R. Combat
Faldon
Fishing Champ
Flyff: Fly For Fun
Freeciv
FreeStyle Street Basketball
Frets on Fire
Gekkeiju Online
Glest
Global MU Online
Golf?
Graal Online
Grand Theft Auto 2
Grand Theft Auto
Gunbound
Gunror
Gunz The Duel
HaloZero
Hero Online
KAL Online
Knight Online World
Kuma\War
Last Chaos
Lunia
Maple Story
Marathon Trilogy
Martial Heroes
Mixmaster
Myth War Online
N
Neverball
Nexuiz
Orbiter Space Flight Simulator
Parsec47
Pirate King
Plasma Pong
Purge
Puzzle Pirates
Racing Pitch
Rappelz
Risk Your Life 2
rRootage
Rumble Box
Rumble Fighter
Savage
Scions of Fate
Scorched 3d
Secrets of Mirage
Shadow Armada
Shadowbane
Shattered Galaxy
Silkroad
Space Combat
Space Cowboy Online
Starsiege: Tribes
Steel Panthers
Strange Attractors
Tantra
Thang Online
The Battle for Wesnoth
The Dinohunters
The Elder Scrolls: Arena
The New Satan Sam
Tickster
Tobolo
Torus Trooper
TrackMania
Transfusion
Tremulous
Tumiki Fighters
Urban Terror
War Rock
Wild Metal
Wolfenstein: Enemy Territory
Xiah
Read more and get the download link from Free PC Gaming Blog