Flash fiction

Last week, the Word Nerd led a discussion with the Oshkosh Area Writer's Club about writer's block.
One participant in the discussion said that the opposite of writer's block would be able to write at any time, any where.
Which brings us to flash fiction.
Rather like JA Konrath's 69 word story contest from last week, flash fiction is far, far shorter than a traditional 2,000-5,000 word short story. Some people classify 55 words as flash fiction. Others will go up to anything less than 1,000 words.
Flash fiction is just what it sounds like -- a flash of an idea, but with a definable plot.
In short, these are the sorts of stories that should be able to be written any time, any where.
This site offers some tips on how to write good flash fiction. The answer here is to be a merciless editor.
Word Nerd would also offer up flash fiction as a solution to all those pesky little ideas running around in a writer's head that either aren't long enough for a full piece or just need to be put on paper so they will stop running around and leave a writer in peace to get on with other writing.
It's not devoted to flash fiction, but Fictional Musings posts only stories under 700 words, and many of these shorts pack a punch.
If you want to try writing flash fiction, try also setting a time limit. What kind of a story can you write in 15 minutes? In 10? In only 5?
If you come up with a good one, post it.