Steam Box today, under the name "Steam Machines." These boxes will come in multiple forms from different manufacturers in 2014, but all Steam Machines will run SteamOS. First, Valve is sending out 300 prototype boxes to Steam users, free, for testing purposes. See if you're eligible here.
"Entertainment is not a one-size-fits-all world," Valve writes. "We want you to be able to choose the hardware that makes sense for you, so we are working with multiple partners to bring a variety of Steam gaming machines to market during 2014, all of them running SteamOS."
Valve announced SteamOS on Monday, a Linux-based operating system designed to play Linux games and stream Windows and Mac games, along with other media, from a computer to the big screen. SteamOS streams over a user's home network and onto a TV using "any living room machine," as Valve put it. "Any machine" now includes the Steam Machines.
Steam's Big Picture, the UI portion of a living room gaming system, entered public beta in September 2012.
Valve founder Gabe Newell has been pitching the Steam Box (in everything but name) as a device to unify mobile, desktop and living room technologies, all possible with a Linux backbone. On Monday, Valve announced that "hundreds" of games are already running in native Linux on SteamOS, and AAA titles are making their way to SteamOS in 2014.
Valve has one more announcement to make this week, in 48 hours.
Update: Valve's final announcement, made on Friday, is the Steam Controller.