"Story Starters" by Scholastic is a flash-based story generator, allowing you to write a short story from virtually nothing. On the first screen, type your name and select your grade -- the game is suitable for kids from kindergarten to middle school. Afterwards, the game takes you to the "story generator," a slot machine combining different elements of a sentence to produce a scenario. If you don't like a specific part of the story, click on "spin this wheel" button to change it. Press "Next" to pick the format of your story (letter, postcard, newspaper, notebook), select if you want to include a drawing and start writing your story.
"Starship" is an online game by the BBC, placing you on a spaceship containing a "story plant." You can scroll over each of the plant's leaves to check its full contents and click on it if you want to add it to your story. Click on the watering can to make the plant grow. Four new leaves appear, from which you can choose the next part of your story. The story always remains incomplete, but you can print what you've opted thus far and finish it yourself.
"Story Spinner" by BonnieNeubauer.com does not help you generate the title of your story or any of its initial parts. Instead, all you get is the setting of your story (where it takes place), the starting phrase, as well as four words you must include on the story. From then on, it is your own task to use these data and come up with an original story. Click on the wheel to get a new setting, opening phrase and four mandatory words.
"Fortune Cookies Stories" at BruceVanPatter.com describes how you can create a story based on the short sentences contained in fortune cookies. The page gives you 10 sentences to start from, while it also mentions how to make up your own random fortune. You can use a fortune cookie sentence to come up with a setting for your story ("The pirate holds the key"), determine the turn of events ("Your sister will ruin your plan") or even use it as a bottom line ("You should eat your Brussels sprouts").