Dreamlords - The Reawakening Type: MMORPG / MMORTS Price: Free, option to pay for more features. Game side: Good Social side: Good Description: It's quite fun, it's like half Age of Empires, half World Of Warcraft. It's still in Beta version (which means it's being created), although you can join anyways.
Cabal Online Type: MMORPG Price: Free, option to pay for more features. Game side: Good Social side: Ok Description: It's like other MMORPG games (World Of Warcraft, Guild Wars...etc) but free.
Well Of Souls Type: MMORPG Price: 100% free Game side: Ok Social side: Excellent Description: If you are looking for a friendly, social game... This is it!
KUMA\WAR Type: MMOFPS Price: 100% free Game side: Very good Social side: Ok Description: It's a lot like Counter-Strike, but free. All maps in it are inspired by real life battles.
I will add some more later, and you can tell me about some you know.