The Games Section on the Frictional Games Website now has a blurb for an "Unannounced project 2" in addition to the Next Frictional Game they recently teased (thanks MajorD). There are even fewer details about this second unannounced project than the first one, which we at least know is Amnesia-related. On a related note, Joystiq has details on Amnesia: A Machine for Pigs, an upcoming collaboration between Frictional Games and thechineseroom (Dear Esther), though it's not clear if this is Unannounced project 2 or something else. Here's a bit:

Set in 1899, Amnesia: A Machine for Pigs follows the "wealthy industrialist" Oswald Mandus, who has returned home from "a disastrous expedition to Mexico, which has ended in tragedy." Struck by a destructive fever, Mandus is haunted by dreams of a dark machine until he mysteriously regains consciousness. Months have passed, unbeknownst to the industry tycoon, and as he emerges from his slumber the roaring engine of a mysterious machine sputters to life.