Modern-day military simulation Wargame: European Escalationis now out for Linux users. If you own it on Mac or PC, you already own it on Linux thanks to Steam. Along with the strategy game being released on Linux, there is also a patch enabling cross-platform play, so PC people can fight against Mac and Linux users.
I love all of this stuff coming to Linux and Mac. I can see a future where PC gaming isn't about what operating system you have, and we can all just play our games together no matter what system we are on.