As has been known for a while now, mostly through excellent (as always) reporting by Phoronix
' Michael Larabel, Valve has been working on porting the Steam client to Linux. Yesterday they opened a blog to keep Linux users appraised of their progress, with promise of regular updates: http://blogs.valvesoftware.com/linux/steamd-penguins/
So if you're interested in Steam games on Linux, head on over and subscribe to the blog
Though they are focusing on Ubuntu 12.04 right now, as a first distro to support, depending on the success of that they will also work to support other distros. Hopefully support for Ubuntu 12.04 will mean the Steam client will run on Linux Mint 13 already as well.