That's right, S2 Games has released Savage 1 for free! It's a great multiplayer game - a mix between FPS and RTS. Two sides (Beast and Human) fight to take control of the map while the Commander of both sides is giving orders and building structures and controlling the players just like an RTS game.
It's easy to learn pick up. But hard to... aim :).
And the best part is: for Linux too.