I heartily recommend the Six Minute Story site. Here you can:
- limber up with a six minute burst of free writing,
- try your hand at flash fiction,
- develop your create-an-instant-story skills,
- work from a selected prompt or from a random prompt,
- read what others have written and comment if you want to.
You may choose a prompt and consider your story options in advance. But once you start typing, the clock starts ticking and you must continue until the time runs out. After 6 minutes, you are forced to stop. There is no second chance to add, edit or to tweak.
When its done, you can save your story and choose a Creative Commons License. Or – if you really want to – you can trash your story.
I prefer to pick a random prompt and I like to start writing without giving myself any time to think. I just see what happens and the only internal ‘editing’ I do is to try to bring the story to some sort of conclusion within the six minutes. Luckily I am a very fast typist.
Here is a link to my latest Six Minute Story: Choosing.