Ron Gilbert's "The Cave" is now available for pre-order on Steam, here. The pre-order price is between US$14.99 and US$19.99 depending where you live (thanks SEGA). There's no firm release date yet, still just "January 2013".
People who pre-order also get some Cave related Team Fortress items.
Update: Looks to be US$14.99 on Greenman Gaming, regardless of territory.