In anticipation of the release of Soma (September 22), Swedish indie developer Frictional Games have launched a promotion on Steam offering Amnesia: The Dark Descent as a free download. If you add the game to your library prior to 6:00pm today it's yours to keep. Furthermore, the Penumbra series and Amnesia: A Machine for Pigs (developed by The Chines Room) are 80% off until September 18. You can also get 10% off Soma's price if you pre-order.
Anyway, Amnesia: The Dark Descent is a game that certainly deserves its spot in your Steam library so make sure you add it before time is up.
For more on Amnesia: The Dark Descent, read our review, and you can also catch up on our impressions of Soma