Wolfenstein: Enemy Territory. It's not really MMORPGs, RPG, Strategy, Card, Etc... but it
is free.
"Wolfenstein: Enemy Territory is a Multiplayer Online First Person Shooter. It's a team game; you will win or fall along with your comrades. The only way to complete the objectives that lead to victory is by cooperation, with each player covering their teammates and using their class special abilities in concert with the others."
This was supposed to be an expansion for RtCW, but was released as a free stand alone version instead.
http://www.3dgamers.com/games/wolfensteinet/