I thought I would just write a little list of new Linux games being developed, it's looking better for Linux gaming these days. We have a bright gaming future ahead.
 
Realtime Strategy with massive battles involving using comets and planets as weapons..
Planetary Annihilation
 
Realtime Strategy in a cyberpunk city setting, this is similar to Syndicate.
Satellite Reign
 
Exploration and survival is the focus in this RPG, looking quite good.
Frontiers
 
Traditional narrative driven RPG, in the style of classic JRPG's.
Celestial Tales: Old North
 
Single and online-multiplayer RPG with focus on immersion and storytelling from Richard Garriot.
Shroud of the Avatar
 
J-RPG
Soul Saga
 
Create and manage your own space program, build your own spacecraft with crazy Kerbals.
Kerbal Space Program
 
Open world RPG with housing, farming and great crafting features.
Balrum 

I'll try to add more as I come across them and all of the above are DRM-free to my knowledge. Feel free to post suggestions of new Linux games, I will look at them and add them.

Indeed, I was considering mentioning Steam as well. I quite like that they have taken the step into the Linux world, even if I don't like the fact that I don't really own Steam games in the same way as DRM-free non-Steam games. But that's another discussion.

Thank you, I should have added KSP already. I have also added a game I found just the other day; Balrum. :)

I like to use Play On Linux to run a lot of my windows games with as well.