This evening, I was excited to open my email and learn that I placed second in the July 2016 100-Word Flash Fiction Competition run by British author Morgen Bailey. She runs these every month, and I have been entering mostly consistently since January. This month my submission, "A Lively Imagination" was chosen from among 23 flash fiction stories to be in the top three. You can read it here.
Each month has its own prompt, which can be integral to or superficial to the story. You have from the first day of the month to the last day of the month to submit a 100-word story that is somehow related to the prompt. Prizes include a choice between certain of the online writing courses Ms. Bailey offers, or a story critique.
Try it out; it's fun!