The Unbirth Website offers the free release of Unbirth from Frictional Games (thanks Gamer's Hell), a project that never got on track as a commercial release, but is being offered in its alpha state due to popular demand. Word is:

To all dear Windows users,

Before creating Penumbra and before founding Frictional Games, Thomas Grip worked on a game called Unbirth, unfortunately this game was never finished due to various issues. Unbirth was a game much like Penumbra, a first person real-time rendered adventure horror game, but without the nifty physics. During the past two years, players of Penumbra has continually asked if it would be possible to release any working code of the game, and well, Thomas decided that it actually is possible!

An alpha version of the game is now released at http://unbirth.frictionalgames.com as well as a short presentation about the game, how it was made and why it was, sadly, never finished. It is an unstable, but working demonstration and gives an insight into the history of the ideas and design choices that was an inspirational source in the creation of Penumbra.