I couldn't find a list of these, so I made one up myself.
STEPHEN KING UNCOLLECTED STORIES
For clarity, this is the list of Stephen King published collections:
People, Places & Things Volume 1 [1960]
Skeleton Crew [1985]
Night Shift [1978]
Different Seasons [1982]
Nightmares and Dreamscapes [1993]
Creepshow [1982] (Graphic Collection)
Four Past Midnight [1990]
Six Stories [1997]
Hearts in Atlantis [1999]
Everything's Eventual [2002]
The Secretary of Dreams Vol 1 [2006] (Graphic Collection)
Just After Sunset [2008]
Stephen King Goes to the Movies [2009]
The Secretary of Dreams Vol 2 [2010] (Graphic Collection)
Full Dark, No Stars [2010]
Published Short Fiction (Excerpts, poems, screenplays, recipes not included)
The Pit and the Pendulum [1961]
[Unknown] 20 page short story about fellow classmates taking of the school [1961]
The Star Invader