Several years ago I read about a competiton at a convention somewhere to write a sci fi story in 8 words. The winning story was brilliant, and I've occasionaly thought of writing something really short myself. Several magazines publish 'flash fiction' of 1000 or even 500 words.
I had a sudden idea last night for a very short story - only 78 words in total. I typed it out and submitted it in record time. Not many markets are looking for work that short, but there are a few.