The dozen companies that have pledged to deliver their own living room PCs / gaming consoles designed around Steam and most likely running their Debian-based SteamOS include: Alienware, Falcon Northwest, iBuyPower, CyberPowerPC, Origin PC, Gigabyte, Materiel.net, Webhallen, Alternate, Next, Zotac, and Scan Computers.
The 12 companies will be showing off their first batch of Steam Machines this week at the Consumer Electronics Show in Las Vegas. The list of partners for the Steam Machines was discovered by Engadget.
As mentioned earlier, sadly this year I am not out at CES like in past years, due to being over in Russia working on Phoronix Test Suite 5.0. There is also a Valve press conference scheduled for later today (5PM PST) where we will hopefully hear new Steam Machines details, etc. Stay tuned for remote coverage on Phoronix.