My brother intruduced me recently to a multiplayer game named
Savage. It's a great mix between a RTS and a FPS.
What is great in this game is the teamplay. You have one commander in your team who act and play like a RTS and the other players are all controling a character like a FPS and the goal is to attack and destroy the ennemy Stronghold. Really worth a try tough I don't recommend it at all to the 56k users.