If you enjoy atmosphere, good mapping, and like to experience genuine fear as inspired in the original Amnesia:TDD, I must suggest the following:
-Followed by Death: Chapters 1&2 (Solid story line, amazing atmosphere is comparable to the original game)
-White Night (a full conversion mod, I think it won best first person mod from ModDB, the story line is a bit cliche, but the atmosphere's good)
-La Caza (won Frictional Game's custom story/mod contest, nice original story line+good mapping)
-One Light in the Darkness (awesome mod, quite a bit of reading, but the atmosphere is good and the mapping is detailed)
If you prefer alternative methods of scares (i.e. jump scares which are generally and regrettably accompanied by poor/sub par mapping), and overall less serious stories, I must offer:
-Dark Room (the original funny map, you're in for quite a surprise!, pretty good mapping actually)
-House of Creep (there are 7 of them I believe; pick your poison
)
I rate it 3 memes.